The mineral kingdom is the base upon which the plant and animal kingdoms have developed. 

And yet it is the least well-known of the three despite the relatively limited number of species that comprise it—a few thousand mineral species identified in 2012 versus more than 10 million for the other two kingdoms!  And just as we have always felt the need to classify all the groups of living creatures so that we might see ourselves within Nature’s profusion and understand its wealth, it is the same for minerals, starting with precious stones and gemstones—the first minerals that really merited man’s attention.  The Persian scholar Al-Biruni (975 -1048), author of one of the oldest books on mineralogy ( الجماهر في معرفة الجواهر), was one of the first to classify precious stones in the eleventh century.  He classified them by density and color, which led him to notice that certain stones then grouped under the same name due to their similar colors, were in fact different because they did not have the same density.  During antiquity for example, lapis-lazuli was confused with sapphire and most green stones were called emeralds.

By the end of the eighteenth century, European chemists had begun to understand that all that existed on Earth was the result of the assembling of simple elements.  By simple element we mean any chemical substance that cannot be broken down into a simpler substance.  From one chemistry experiment to another, scientists have discovered 88 natural elements of the 118 currently known. The extra 30 elements are radioactive and have a short life, typically less than one hundred million years.

And so, every mineral is a combination of these elements.  Among the Earth’s most abundant minerals, silica is a silicon oxide (SiO2), limestone a calcium carbonate (CaCO3), orthoclase an aluminosilicate of potassium (KAlSi3O8), etc.  As can be seen, it is logical to try to classify the mineral world according to its chemical composition.

But there are several ways to classify minerals.  The first were based on the artistry of the miner and then by that of the metalworker, often associated with the blacksmith.  And so we find classifications where the criteria are: hardness (even if numerous species have the same hardness); color (though the same mineral can present several different colors), the resistance to shock (a delicate question); resistance to heat; crystal shapes (unfortunately, rarely well-developed or visible), and the type of mineral deposit, etc.  Finally, it was the chemical classification system proposed by the Swedish scholar Berzelius that mineralogists chose for their first trials.  This system presents fewer disadvantages than the others and yields 9 classes:

Class 1 - Natives and Alloys (for example: gold, silver and platinum)

Class 2 - Sulfides and Sulphosalts (examples: pyrite, galena)

Class 3 - Halide(examples: halite, fluorite)

Class 4 - Oxides and Hydroxides (examples: corundum, hematite)

Class 5 - Carbonates and Borates (examples: calcite, rhodochrosite)

Class 6 - Sulfates, Chromates, Molybdates and Tungstates (examples: gypsum, barite)

Class 7 - Phosphates, Vanadates and Arsenates (examples: apatite, mimetite and vanadinite)

Class 8 - Silicates (examples: quartz, topaz, beryl)

Class 9 - Organics (examples: mellite, whewellite)

The mineral world is composed of a relatively limited number of these chemical substances.  Indeed, today we count around 4,500 minerals on the Earth’s surface, compared to the billions (or more) of different organic molecules produced by living creatures.  The mineral world is also much simpler than the organic world: the DNA molecule that is the basic component of every living being contains several hundred million atoms --carbon, hydrogen, oxygen, nitrogen, phosphorus— while the chemical formulas of the most complex minerals do not exceed a hundred or so atoms with the most common having no more than a dozen!

But the chemical classification system proved to be insufficient because the same chemical formula can take on different aspects.  Carbon offers the most striking example: this element can appear in the form of graphite, one of the tenderest solid bodies known, or again as a diamond, the hardest known solid body on Earth.  Another example is calcium carbonate, which exists in two main forms: calcite, which makes up limestone (among others), and aragonite (found in pearls, etc.)

The secret to these differences lies in the way the atoms bond and arrange themselves to build, as the case may be, a graphite crystal or a diamond crystal, or again calcite or aragonite.

Indeed, the most impressive aspect of the mineral world is the fact that the atoms of a given material arrange themselves in a very orderly fashion to make up a solid body.  Why do atoms organize themselves in this way, in a structure so regular, or periodic (the two terms are synonymous), like the cobbles in pavement?  Is it the most compact way to arrange them, Mother Nature always looking to economize her efforts?  There are a lot of intuitive responses, but scientists are still unsure.  To measure the complexity of the phenomenon, consider the challenge of arranging marbles, all of them the same, in the most  compact pattern possible—a mathematical problem formulated by Kepler in the seventeenth century to explain the hexagonal shape of some snowflakes:  Just think of the pyramids of oranges at a fruit stand.  It was not until 1998 that a mathematician was able to demonstrate, almost completely, that maximum density is indeed reached, as orange sellers have long known, with stacking in pyramidal form.  The demonstration was not totally completed until 2011!  But oranges present nothing more than practically identical spheres.  So, we are still a long way from demonstrating the general case where atoms make complex bonds with other atoms of different sizes.  Whatever the case, and with few exceptions, the atoms of a solid are not arranged just any way.  They respect a certain order: distances between atoms are regular with precise values and orientations for each species.

This organization, called crystalline structure, presents itself in geometric forms and volumes limited by flat segments called faces.  These volumes are what we call crystals.  An analysis of these forms, which the surveyor calls crystal polyhedrons, shows that we can classify them according to the different orientations of similar faces.

The symmetry in this stacking of each atom can be found in the crystal which results from it. More generally, it has been shown that 32 possible crystal symmetry groups exist that give a limited number of ideal shapes that crystals can take in the natural world, of which the most recognizable are the cube and the hexagonal prism.  These different possibilities therefore help us to refine the chemical classification.  Thus, the diamond is crystallized carbon in cubic form, while graphite is always carbon crystallized in a hexagonal shape.

Of course, these classifications exist alongside the characteristics remarked by the ancients, such as hardness, optical properties, and density, etc., but also the characteristic and regular distances between the atoms, since we learned to measure the latter during the twentieth century.

In summary, a mineral is characterized by the chemical formula that defines the proportions of the elements of which it is composed, as well as by the stacking of these element’s atoms following one of the 32 symmetry groups.  For example, beryl is an aluminum and beryllium silicate with a hexagonal system of crystallization.  Sometimes this mineral presents itself in different colors due to the impurities it contains, and so a name is sometimes given according to the species to which it belongs.  For example, beryl in a beautiful dark green color is called emerald, while blue beryl is called aquamarine.

Class 1 - Natives and Alloys

Class 2 - Sulfides and Sulphosalts

Class 3: Halides

Class 4 - Oxides and Hydroxides

Class 5 - Carbonates and Borates

Class 6 - Sulfates, Chromates, Molybdates and Tungstates

Class 7 - Phosphates, Vanadates and Arsenates

Class 8 - Silicates

Class 9 - Organics

Class 1 - Natives and Alloys

By “element” chemists mean chemical bodies that cannot be broken down into other, simpler bodies.  For example, water is a molecule that can be broken down into oxygen and hydrogen which cannot be broken down further.  Therefore, water is a composite body while oxygen and hydrogen are elements.  There are 88 known natural elements that constitute all known matter on Earth, most of the time in the form of composite forms, plus 30 elements artificially created by man, all radioactive (the most famous being plutonium).  Within these elements we can distinguish two big families: metals and non-metals.  The frontier between these families includes semimetals such as antimony and semi-conductors like silicon.  In mineralogy, the definition of the family of the “native” elements is not so strict.  In this family we can find metals (generally somewhat impure), but also alloys and amalgams that are combinations whose formulae are generally well-defined, as well as a few notable rarities such as carbides, phosphides and nitrides.  

This family is not very wide-spread and represents around 3 to 4% of the known species in mineralogy.

The native metals are quite rare on Earth.  Most of the time, metals are found in minerals combined with oxygen (the oxides), sulfur (the sulfides), silicon (the silicates), etc., and the difficulty in metallurgy is to extract them.  However, some metals exist in a native state: among the oldest known to man are copper, silver and gold.  Gold for example is found in round nuggets in rivers or more rarely in crystals containing not more than 75 to 80% gold (the rest being silver, copper, palladium, etc.).  Even impure, at a first glance gold crystallizes as if it were pure.  The collection presents a selection of the best gold samples from California and Venezuela, as well as copper from Michigan in the United States.  Some large gold deposits, like those in South Africa and Nevada (USA) are not well-represented because more generally in microscopic form disseminated in another mineral: only 0.4 grams of gold per ton of ore in the big deposits of Nevada!  These deposits are the main sources of gold but require heavy processing treatments that generate much pollution, such as the use of potassium cyanide, a violent poison.  It is one of the many paradoxes of this fascinating metal: the deposits where it is visible in beautiful crystals often possess small quantities of gold, while those where the gold is invisible can be very rich.  (Nevada alone accounted for about 10% of world gold production in 2010.)  The external crust of the Earth, about 16 kilometers thick, appears to contain some twenty billion tons of the yellow metal.  Another eight billion tons is thought to exist in diluted form in the water of the world’s oceans.  It is estimated that 167,000 tons of gold have been extracted as of end-2010, around two-thirds of it during the last two hundred years.  If we made a cube of all the gold that has been extracted since the dawn of humanity, it would only be 20 meters a side!

Another precious metal, whose importance in industry is even greater than its role in jewelry-making, platinum, is also well-represented in the collection.

Native iron is quite rare.  It can be found as an alloy with, among others, nickel in meteorites (like those exhibited from Nandan in China’s Guangxi province).  Native lead is also rare and is represented by well-crystallized samples.  The collection also exhibits one of the best specimens known of a natural amalgam of mercury and silver --comparable to amalgams made by man to fill dental cavities—moschellandsbergite from Germany.

Among the least rare of the non-metals is carbon, represented in the collection by one of the three largest diamonds known, although not much use in jewelry because of the rareness of its transparent zones.  There is also sulfur in beautiful yellow crystals from Italy, arsenic, antimony (the collection has a Canadian specimen with the most beautiful crystals known), bismuth (one of the most beautiful samples from Germany) and tellurium.

Class 2 - Sulfides and Sulphosalts

This family accounts for 15% of known mineral species.  It is often represented in collections because it includes many minerals of considerable industrial importance.  In fact, most of the ores of copper, lead, silver, zinc, cobalt and molybdenum, etc. are sulfides.  These minerals are usually found in what are called metalliferous veins, or lodes, that have been actively sought after and exploited since the Bronze Age, even when their dimensions were rather modest.  Pyrite (iron sulfide) is by far the most frequent sulfide and has been used not only as a flint stone for lighters, but also as sulfur ore to make the sulfuric acid so essential in the chemical industry—that is until we found out how to extract sulfur in natural gas and petroleum.  Sulfides often have a golden or silvery metallic appearance with shiny, flat faces and amazing geometric shapes.  Relatively abundant, they are very popular in collections.

The collection boasts a rich selection of numerous, high-quality sulfide specimens found either in historic mines like those of Mexico, England or Saxony in Germany, or again in modern mines (in the Congo, Russia, China, etc.).  We cite as examples argentite and pyrargyrite from Mexico, among the most beautiful known, as well as carrolite from the Congo, proustite from Chile and Saxony, the most beautiful geocronite ever found (from Brazil) , and one of the best cubanite specimens from Canada.  We also find specimens that make an honorable showing thanks to their uncommon dimensions or esthetics: molybdenite from Australia; arsenopyrite from Portugal and China; stibine, kermesite and kesterite from China; galena and sperrylite from Russia; pyrites presenting rather unusual forms (from Mexico and Peru), and many more.

From the point of view of chemistry, this family includes two sub-families:

Sulfides:  For example, pyrite is an iron sulfide, noted as FeS2  (that is for each atom of iron there are 2 atoms of sulfur).  The iron in this formula is called cation and appears at the right of the chemical formula.  Sulfur is called anion and appears at the left of the chemical formula.  What we call a sulfide in mineralogy is a little more general: a mineral in which the anions are one or more atoms of sulfur, selenium, tellurium, arsenic, antimony or bismuth.  In this case we speak of sulfides (by far the most numerous in this family), selenides, tellurides, arsenides, antimonides and bismuthides.

Sulphosalts: this sub-family includes minerals in which the anion is sulfur combined with arsenic, antimony, bismuth, germanium or tin.  In this case, we speak of sulpho-arsenides, sulpho-antimonides, sulpho-bismuthides, sulpho-germanides or sulpho-stannides.  Other minor anions are also admitted into this family, such as chlorine and oxygen.   Thus, kermesite, an oxysulfide of antimony, Sb2S2O, belongs to the sulfide family.

Class 3


This family accounts for around 5 to 6% of known mineral species.  Few halides are represented in museums because many of them prove difficult to conserve: they are often quite sensitive to humidity.

The most abundant ore in this family is halite, a sodium chloride (NaCl) better known under the name of rock salt, which is extracted on land from mines and is practically identical to salt extracted from the sea.  The collection possesses two such specimens from Poland.  But fluorite (calcium fluoride, CaF2), not as well-known to the public, is by far the most popular halide with collectors.  It can often be found in beautiful transparent crystal; it stays perfectly conserved, and is what some call a “rainbow” mineral because it can take on all the colors.  It is also abundant, initially encountered in metalliferous veins, and has always been avidly sought-after.  For its colors, fluorite has long been used in decoration: Roman vases, some of the columns of the Paris opera house, and Chinese statuettes.  Today fluorite is an important industrial ore used as a fluxing agent in metallurgy (for making aluminum and steel, purifying uranium, etc.).  Or again, it can be used to obtain fluorine used in the manufacturing of special plastic materials: Teflon and Gore-Tex are 76% fluorine!  Fluorite is also a component in refrigerant gases used in air-conditioners and refrigerators.  The collection exhibits a beautiful selection from famous deposits that have earned the esteem of collectors: no fewer than 12 countries are represented.  And the specimens present a broad palette of colors.

The collection also possesses the second most well-known ensemble, by virtue of its dimension and the quality of its specimens, of an extremely rare mineral: cumengite (the number one specimen being that of the Sorbonne-UPMC collection in Paris).  This mineral appears in the form of groupings in a star pattern, rather exceptional in the mineral world.  It also includes quality specimens of rare species such as iodargyrite, atacamite and cryolite.  

Chemically speaking, this family includes minerals that are a combination of metals and halogens.  Halogens are a family of chemical elements having similar properties, the most well-known of which are chlorine and fluorine.  We also find iodine and bromine, though iodides and bromides remain quite rare in the mineral world.  There can be additional groupings of atoms with a chemical role close to that of halogens, and which we call anions.  We thus find other anions such as hydroxyl (OH), oxygen, sulfate or nitrate ions.  Atacamite, Cu2(OH)3Cl for example, is a hydroxyl chloride of copper classified with halides, and not with oxides or hydroxides.

Class 4 - Oxides and Hydroxides

In the current classification, this family represents around 14% of known minerals.

It is a family of utmost importance in industry because it is here that we find the minerals that make up the most abundant ores in iron (hematite Fe2O3 and magnetite Fe3O4, 1.5 billion tons extracted every year); aluminum (diaspore); tin (cassiterite, which the Phoenicians went as far as England to extract in order to make bronze); titanium (rutile and ilmenite); uranium (uraninite); or rare metals such as tantalum, used in electronics (tantalite). We also find in this family precious stones and semiprecious stones of importance (rubies, sapphire, spinel and chrysoberyl).

The collection possesses several specimens of oxides of high quality.  Some belong to common species such as hematite (large crystals from Brazil and brilliant crystals from South Africa); cuprite (among the best crystals from Namibia and Australia); Chinese cassiterite; some of the most beautiful rutile specimens from Brazil in the form of daisies; and manganite from Germany.  Others belong to rarer species like uraninite and manganotantalite (the most beautiful known crystals from Afghanistan), valentinite (the most beautiful specimen known from Bolivia), brannerite, ixiolite, thorianite, or even stottite (only found in Tsumeb in Namibia). The MIM also possesses beautiful specimens of precious or semiprecious stones that were saved from the cutter’s blade: rubies and sapphire from Tanzania, sapphire from Sri Lanka, rubies and spinel from Myanmar and one of the most beautiful chrysoberyl twins from Brazil.

From a chemical point of view, this family includes minerals whose anions are oxygen or a hydroxyl ion (OH). The MIM possesses one of the most beautiful specimens of manganite which, with its formula MnO(OH), can be considered at the same time an oxide (O) and a hydroxide (OH).  In general, this family includes minerals where the (O) and (H) blocks have been partially replaced by fluorine or chlorine.  Just where this family ends is not very clear and is a subject of argument among some specialists because oxygen, which makes up 50% of the Earth’s crust not including the atmosphere, can already be found in most minerals.  Thus, tantalite, niobate, certain titanates, some antimoniates and uranates, selenite, arsenite (but not arsenates), tellurite and iodates are considered to be oxides.  Some mineralogists consider,     too, that tungstate, molybdate and chromate –currently forming a sub-family of the class VI sulfates—should be counted in as oxides.


Class 5 - Carbonates and Borates


This family accounts for around 9% of known species.

Several carbonates play an important role in the composition of certain rocks, particularly in countries of sedimentary origin like Lebanon.  Limestone, present everywhere, is mostly made up of calcite, that is calcium carbonate.  The white dolomite of the Batroun region is rock made up essentially of dolomite, a calcium and magnesium carbonate.  The minerals in these rocks appear in the form of microcrystals that are too small to rival the calcite and dolomite specimens exhibited in the collection.   These carbonates are essential construction materials (building stone, marble) and are also the basic raw materials for making cement, lime and glass, etc.  We also find in this family ore constituents more or less important such as siderite ---long a source of good quality iron, more or less combined with magnesium— or smithsonite (from which we get zinc).  The collection possesses a rich series of carbonates that are among the best ever found: calcites --by far the mineral that exhibits the greatest variety of shapes— from 13 different countries with a wide variety of forms, sizes, twinned crystals and colors.  Also on display are rhodochrosite from Colorado (USA); cerusite from Morocco and Namibia (with the most beautiful twin ever seen, in the shape of a heart); smithsonite from Namibia; spectacular siderite specimens from France; aragonite from Slovakia; phosgenite from Morocco and Italy; and the list goes on.

The collection possesses some rarities such as weloganite from Canada, a chemical rarity found only in Quebec.  Other rarities include beautiful specimens of crystallized bastnaesite, which in the last few years has become one of the principal sources of a whole series of metals called lanthanides – essential in high technologies.

From a chemical point of view, the carbonate anion is formed from one carbon atom and three oxygen atoms, with the formula CO32-. The foreign anions tolerated in the carbonate family are principally the ions hydroxyl (OH-), chloride (Cl-), fluoride (F-) and sulfate (SO42-).  All carbonates are more or less sensitive to acids, with release of carbonic gas, but they conserve well.


Borates are relatively rare, as the boron that is the main element is not very abundant in the Earth’s crust.  It is a small family that accounts for around 2% of known species. For this reason, and also because of vague chemical similarities, it is traditionally included in the much larger carbonate family—a somewhat arbitrary choice.

A great number of borates are hydrated and can be found in deposits resulting from the evaporation of saline solutions in arid regions.  The principal borate, called borax (sodium borate), has long been used to make soap and glass and was harvested mainly from the lakes of Asia Minor and Persia.  Its name comes from the Arabic (بورق), which in turn comes from the Persian (بوره). These hydrated borates are, for the overwhelming majority, unstable and have a strong tendency to disintegrate as they become dehydrated.  But they can be conserved by strictly controlling humidity and temperature.  Other borates, smaller in number, are not hydrated and are found, for the most part, in pegmatite (rock similar to granite, characterized by its large crystals).  Contrary to hydrated borates, pegmatite borates are resistant and can be conserved without difficulty.  However, they are rare minerals, known to be in very few deposits and avidly sought-after by collectors.

Hydrated borates’ instability is the reason for which the collection only possesses a single specimen: a large kurnakovite from California.  On the other hand, the collection has a beautiful series of anhydrous borates that includes one of the largest and most beautiful jeremejevites known from Namibia, beautiful hambergites from Afghanistan and Madagascar, handsome rhodizites and londonites from Madagascar, and a rare painite from Myanmar among others.  

From a chemical point of view, the borate family mainly includes minerals whose anion is either the borate ion (BO33-) or groupings that are more or less complex associating boron and oxygen.  The hydroxyl ion (OH-) is tolerated and, as in other families, so are some other anions—as long as they remain minor.  Borates have sometimes been classed with carbonates, but according to the arrangement of the groups of ions borates have also been subject to a more precise classification after the example of silicates.  And so we find nesoborates, soroborates, inoborates, phylloborates and tectoborates.  Another classification system distinguishes between mono, di tri, tetra, penta, hexa, hepta and megaborates.

Class 6 - Sulfates, Chromates, Molybdates and Tungstates


This family includes around 10% of known minerals.  In spite of this percentage, sulfates are not well represented in collections due to difficulties with conservation.  A great number of sulfates are products of oxidation of sulfides in water and are therefore hydrated.  So they present the same challenges as halides and certain borates, that is to say they are very sensitive to an atmosphere that is either too dry or too humid.

The best-known mineral in this family is certainly gypsum, or plaster stone.  It is a hydrated calcium sulfate (CaSO4.2H2O).  When heated, it loses part of its water content and becomes plaster in powder form.  When water is added to the powder, the gypsum reforms and crystallizes.  The interlocking of reformed crystals ensures the structure’s solidity.  This is the principle of all cements that are, most of the time, silicates that behave like sulfates.  Gypsum crystals are very frequent and in Mexico they can measure several meters in length.  The collection exhibits a series of high-quality gypsum in various forms.

Barytine, celestite and anglesite form a small sub-family of sulfates that are anhydrous and chemically stable but susceptible to shock.  They are much prized by collectors.  This collection possesses some fine samples in rather varied shapes and colors.  In addition to these classic sulfates, there are several high-caliber rarities such as leadhillite from Namibia (one of the best specimens known), the best spangolite known and a handsome brochantite from Mexico sporting rather large crystals for its species.

From the point of view of chemistry, this family is characterized by the presence of the sulfate anion, made up of one atom of sulfur and 4 atoms of oxygen, with the formula (SO4--). The hydroxyl ion (OH-) and halide ions like (F-) or (Cl-) can also be present as long as their presence remains incidental.

Chromates, Molybdates, Tungstates

This is a very small family, sometimes included in the family of sulfates and sometimes with the oxide family.  It accounts for only 1.5% of known species.  But it also includes minerals of considerable industrial importance such as wolframite, ferberite, hubnerite and scheelite, the principal sources of tungsten.  The latter is a very dense metal (as dense as gold) and also very resistant (it melts at 3,400°C).  It is for this reason that it is used to make lamp filaments, though it is mainly used to make special types of steel, cutting tools (tungsten carbide), etc.  Well-crystallized specimens are rare: these minerals usually appear as stony masses.  For example, large scheelite crystals were only found in Korea until extraordinary orange-colored crystals from China appeared in the 1990’s, considered until then to be quite rare (the Korean samples were often black).  One molybdate, powellite, isn’t found in large well-formed crystals outside of some Indian deposits, and this since the 1990’s.  The collection possesses high-caliber specimens of these minerals, including beautiful hubnerite samples from Peru, orange scheelite and a rare well-crystallized red scheelite from China, as well as large, perfectly crystallized powellites from India on needles of scolecite.

This family also includes two minerals that are considered to be among the most remarkable creations of the mineral world and are therefore much sought after by collectors for their amazing colors and luster.  These are crocoite (a lead chromate) and wulfenite (a lead molybdate).    Crocoite is a rare mineral, found in few deposits.  The collection possesses two of the most characteristic samples produced by the mines of Tasmania in Australia.  Wulfenite is a typical mineral associated with the principal ore in lead, galena (a lead sulfide), which becomes wulfenite under oxidation.  Several wulfenite specimens constitute the highlight of the exhibit.  Specimens from Mexico are classified among the best ever known from such deposits, and those of Colorado (USA) are also characteristic of that famous deposit.  There are also some remarkable rarities like szenicsite (among the best examples known) and stolzite (in large crystals found in a small mine in the Lozere region of France).

The anions of the minerals in this sub-family are CrO4- -(for chromates), MoO4- -(for molybdates), et WO4- -(for tungstates).  Because of these anions’ resemblance with sulfates (SO4- -), these minerals have been classed in a sub-family next to sulfates.  But some mineralogists propose including them in the oxide family.

Class 7 - Phosphates, Vanadates and Arsenates

This family represents around 16% of known species.

Some of the minerals in this family are formed in the superior zone of metal veins exposed to rain water infiltration, oxygen and bacteria.  This zone is called the “iron cap” due to its red color left by iron oxides.  Iron caps are easy to find and mine, but they are not generally wide-spread.  One often finds there hollow cavities in which crystals have developed freely.  And as these iron caps are becoming increasingly rare due to intense mining, so too are the minerals found there.  The presence of certain metals that are naturally concentrated in iron caps –such as iron, copper, vanadium, or uranium—present attractive colors in many species.  These colors combined with well-formed crystals in groupings of exceptional beauty make many of the minerals of this family among the most sought-after, even if they are often quite fragile.  This collection possesses some of the most beautiful vanadinite specimens from Morocco in perfect red hexagonal prisms on a white gangue.  Also exhibited are amazing green pyromorphites from China, mimetite from China and Australia, erythrite from Morocco, the most beautiful specimens of legrandite, scorodite and adamite from Mexico, amazing phosphophyllites from Bolivia, as well as a rarity found only in Tsumeb (Namibia): ludlockite.  

Some phosphates can also be found in different contexts linked to cooling of melted rock (magma).  Such is the case for pegmatite phosphates, which are in general not as fragile as phosphates from iron caps but are less colorful.  They give well-crystallized specimens in what specialists refer to as crystal crypts.  In the collection, one can admire some of the most handsome specimens of herderite and Brazilianite from Brazil, apatite from Portugal and herderite from Pakistan.

Finally, phosphate, vanadate and arsenate ions all share a strong chemical affinity with uranium and form with this metal several minerals characterized by their brilliant colors.  The collection possesses a series of some of the best such minerals known from the Congo, Gabon, Brazil and France.

From a chemical point of view, this family is characterized by groupings composed of one ion of phosphorus (P), arsenic (As) or vanadium (V), and 4 atoms of oxygen.   Thus, phosphates contain (PO43-) in their formula, arsenates (AsO43-) and vanadates (VO43-). The hydroxyl ion (OH-) and halogen ions also appear in certain species.  There can also be substitution between phosphorus, vanadium and arsenic.

Class 8 - Silicates

These are the minerals whose composition includes silicon bound to oxygen.  Considering that these two elements alone make up 75% of the Earth’s crust, it is not surprising that this family is the most abundant (25% of known minerals) and one of the most complex.  The chemical formulas of silicates are often quite close, and to classify them, structural data had to be introduced.  The starting point is a structural unit formed of one atom of silicon surrounded by 4 atoms of oxygen and whose positions are represented by a geometric shape of 4 faces in isosceles triangles: this is what we call the “SiO4 tetrahedron”.  In silicates, the presence of foreign ions modifies the arrangement of the bonds between the tetrahedrons.  Based on the how the tetrahedrons are arranged among themselves, we can define several sub-families.  Numerous foreign anions can be present: the hydroxyl ion (OH-), halides (F-) and (Cl-), sulfates (SO42-) and carbonates (CO32-), etc.


Silica is a silicon oxide.  It should normally be classed with oxides, but can also be classed among the silicates as silica is formed entirely from tetrahedrons that are bound according to a dozen different structures depending on temperature and pressure: quartz, tridymite, cristobalite, stishovite and coesite.  Only quartz exhibits spectacular specimens, the other varieties being in general microscopic.  In fact, the term quartz includes two minerals of different geometrical structure: alpha quartz, stable at low temperatures, and beta quartz which remains stable at temperatures exceeding 573°C.  All of the quartz crystals exhibited at the MIM have an alpha quartz structure, but the crystals initially formed at temperatures exceeding 573°C exhibit faces that tell of an ancient beta symmetry.  Quartz that has formed at lower temperatures does not present these faces.  Quartz is the main component of sand: small grains of sand are in fact tiny eroded crystals.  It is an essential raw material for making glass, cement and silicon (the basic material of all modern electronics).  Quartz has always been found in large, colorless crystals in the shape of hexagonal prisms with pointed ends (rock crystal) and has been used since the Fatimid era to carve magnificent dishware (ewers) and jewelry, either in violet (amethyst) or smoky-colored crystals.

The collection possesses a selection of very high-quality quartz from Brazil, in particular the most beautiful twinned crystal ever found, called Belovda, and resembling a Japan-Law twin but with a different angle.  There is also exceptional quartz from France, Switzerland, the United States (a rare twin of smoky quartz), Russia and China; amethysts from Mexico (also a rare twin), Brazil, Namibia, etc.  Quartz also appears in the form of “twisted” crystals called gwindel, well-represented in the collection.

Finally, the collection exhibits a beautiful opal from Australia: a type of hydrated silica made up of tiny joined balls of silica, either amorphous or only slightly crystallized.  When the beads typically reach a diameter of between 0.2 and 0.3 microns and are well-stacked, the mineral gives an amazing multi-colored optical effect that changes according to the direction of observation.


The term neso is derived from the Greek word for isle. Nesosilicates are characterized by tetrahedrons (SiO44-) that have no bond between them, as these bonds are made with foreign ions.  This is why we find the notation SiO4 in their formula.  Such is the case of peridot, for example (Mg,Fe)SiO4, which gets its name from the Arabic فريدة  even if this mineral is always called    زبرجد in that language and is cited as such in a Hadith:

أجاب الرسول: الكوثر نهر يجري تحت عرش الله, ماؤه أشد بياضا من اللبن, وأحلى من العسل, وألين من الزبد, حصاه الزبرجد والياقوت والمرجان, حشيشه الزعفران, ترابه المسك الأذفر, قواعده تحت عرش الله عز وجل

…God’s messenger answered: “The Kawthar is a river that flows under the throne of God. Its water is whiter than milk, sweeter than honey, softer than foam; its stones are peridot, ruby and coral, its grass is saffron, its sand is fragrant musk.  Its foundations are established under the throne of God Almighty.”

This sub-family accounts for around 5% of known mineral species.  We find in its ranks several major mineral constituents of certain rocks.  Such is the case for the olivine family, which includes forsterite, peridot and fayalite and makes up most of the rocks called peridotites.  (Nowadays, it is thought that the rocks of the Earth’s mantle situated under the crust are for the most part peridotites.)  The garnet family (البجادي )  includes some fifteen species, some of which are typical in certain rocks.  For example, almandine garnet forms in eclogite and in mica-schist, while spessartine garnet forms in pegmatite.  Zircon, which gets its name from the Arabic زرقون (signifying vermillion) and derived in turn from the Persian  زرگون signifying the color of gold, is found in a great variety of rocks.  It is a very stable mineral that resists all forms of erosion and Earthly transformations, to the point that some crystals are among the oldest known to exist (more than 3 billion years), thus revealing precious information on the history of our planet.  Peridot, garnet and zircon are also used as prized semiprecious stones when they are sufficiently pure and colorful.  And today zircon has become the essential raw material for making high-performance ceramics, special types of steel and alloys for the nuclear industry.  As a general rule, nesosilicates belong to high-symmetry crystalline systems.  Their hardness and a high refractive index make them beautiful stones for jewelry when they are transparent.  

The collection possesses a number of specimens of high-caliber nesosilicates.  An ensemble of high-quality garnets can be found, among them grossulaires from Quebec and Mali, spessartine from Pakistan as well as rather esthetic specimens from China and amazing ones from Brazil.  Of those specimens that stand out for their perfection or their dimensions, we need to mention cuprosklodowskite from the Congo, one of the best ever found; one of the most beautiful euclases known in an amazing blue-green and facetted by nature like a carved precious stone; a rare green zircon twin from Sri-Lanka, partially transparent; a large zircon from Australia that is 732 million years old; and one of the most beautiful green sphenes from Brazil (the word sphene comes from the Greek for “corner”, origin of the Arabic   سفينة and إسفين), etc.

The range of topazes is representative of the different qualities presented by this mineral.  We can find the superb imperial topaz from Brazil that is much appreciated in jewelry; blue topaz from Russia and Brazil (of which one of the most beautiful, in an amazing blue and perfectly crystallized weighing 25,000 carats!); amazing champagne-colored topaz, perfectly limpid, from Pakistan (unfortunately, the color is unstable in daylight and therefore must be exhibited under light poor in ultra-violet rays).


The term soro comes from the Greek word for mass or cluster.   In this sub-family we find  SiO4 tetrahedrons bound by pairs in a common peak, thus forming  Si2O7  groupings or more complex groupings of  3 or 5 tetrahedrons. Additional isolated tetrahedrons may also be present.

This sub-family represents around 3% of mineral species.

Sorosilicates offer up few specimens worthy of being exhibited in a museum.  Among them we find hemimorphite (a zinc silicate), which looks a lot like smithsonite (zinc carbonate), and these two minerals are often grouped together by miners under the name calamine.  Of the known minerals in this family we find epidote, a rather typical mineral in certain rocks found in fissures in alpine-type mountain ranges (the Alps, the Andes and the Himalayas) and in the form of rather beautiful and brilliant crystals.  The mineral is highly coveted by collectors.  The same is true of vesuvianite, which produces a few very colorful varieties, and of axinite (sometimes grouped with the cyclosilicates).

The collection possesses several highly interesting sorosilicates, both from an esthetic and a mineralogical point of view.  Esthetically speaking, epidote is well represented by a classic piece from Austria and more recent, and equally esthetic, specimens from Pakistan.  Vesuvianite specimens from Quebec reputed to be the most handsome are represented by very high-caliber pieces, and those from Italy by a classic piece of perfect geometric proportions.  Zoisite, similar to epidote, is known through one of its varieties, tanzanite, which is one of the most fascinating minerals by virtue of its 3 colors depending on the axis of observation (blue, violet and red), and has thus become quite popular in jewelry-making.  The collection possesses a series of high-quality tanzanites, including a free-form crystal that is enormous for its species.  There is also a large axinite specimen from Russia.  From a mineralogical point of view, the most important species is by far chevkinite, a rare species with well-defined crystals, which to date has been found in only one location in Pakistan in beautiful specimens of which the collection conserves two of the best ever found.


The term cyclo comes from the Greek work for ring.   In this family, the SiO4 tetrahedrons are organized in rings, Si3O9, Si4O12 or Si6O18 (rings with 8, 9 or 12 atoms of silicon are also known but rarer).

This sub-family accounts for around 2% of mineral species.

Few cyclosilicate species are exhibited in the collection.  However, these minerals are rather attractive and come in a great number of varieties.  The most prestigious species is beryl, of which the most popular varieties in jewelry are blue (aquamarine), green (emerald), pink (morganite), colorless (goshenite), yellow (heliodore) or red.  The opaque varieties are used as beryllium ore, a light and very resistant metal used in aeronautics and in space travel and that is an extremely rare element on Earth.  There are 3 tons of beryllium for every million tons of Earth’s crust, which makes finding beautiful crystals within it nothing short of miraculous.  Two of the eleven species of the tourmaline group –elbaite and liddicoatite—are known for their wide range of colors; they are sometimes qualified as “rainbow” minerals.  Mineralogists and specialists in precious stones have agreed on different names for differently colored minerals: rubellite (red), verdelite (green), indicolite (blue), and achroite (colorless: paradoxically the rarest of varieties).  The other tourmaline species generally produce dark or black stones like that of schorl, which is by far the most frequent species in this group.

The collection possesses an ensemble of cyclosilicates of international fame: beryl (one of the most beautiful collections of aquamarine with spectacular pieces from Pakistan, including a large bouquet of some fifty crystals of rare beauty; some of the most handsome morganites from Brazil and Afghanistan; a series of emeralds from Colombia, too light in color to be carved, which saved them from the chisel, but nonetheless in spectacular green, etc.).  The collection also exhibits one of the best series of a recent and very rare species related to the beryl group: pezzottaite.  Tourmaline is also very well represented: the most beautiful rebullites from Brazil; verdelite and indicolite from Afghanistan; liddicoatite from Madagascar, with complete crystals but also in fine, polished pieces showing the incredible geometry at the heart of these crystals that are only found in few deposits on that island.

In addition to beryl and tourmaline, there are other spectacular cyclosilicates like dioptase and benitoite.  Dioptase’s deep green color makes it one of the most sought-after minerals.  The collection possesses one of the most beautiful specimens to have ever come out of the famous Tsumeb mine in Namibia, with a brilliant contrast between the green of the crystals and the white of the rock on which they developed.  Sheets of benitoite crystal associated with neptunite on white rock are considered to be the best ever known for this species and have been found in only one location in the United States.


The term ino is derived from the Greek word for fiber. In this family the tetrahedrons organize themselves in chains of SiO3, [SiO3]2, [SiO3]3 or more (the absolute record for natural minerals is the chain [SiO3]12). Tetrahedrons can also organize themselves in ribbons resulting from condensation of two chains.  The most frequent ribbon is Si4O11. There are also more complex arrangements in multiple chains, columns, tubes, etc.

This sub-family represents around 4.5% of mineral species.  It consists of two groups of minerals essential in the composition of rocks: pyroxenes or tetrahedrons arranged in chains (more than 20 known species), and amphiboles or tetrahedrons organized in ribbons (more than 65 species known).  These minerals can be so abundant that certain rocks have been baptized pyroxenites and amphibolites.  All the minerals in these two groups have fibrous varieties, collectively called asbestos.  Asbestos exhibits amazing mechanical and thermal properties long exploited in industry until it was discovered that it seriously damaged the lungs of people who had breathed in the fibers.

The most beautiful examples of inosilicates in this collection are kunzites from Pakistan and Brazil.  (Kunzite is the pink and transparent variety of a pyroxene that is normally stony, called spudomene, a lithium ore used in modern batteries.)  The collection possesses several high-caliber pieces, one of which in association with a magnificent morganite from Afghanistan.  Other excellent examples of inosilicates are arfvedsonite from Malawi; ferro-actinolite from Pakistan (from a one-time discovery that yielded few samples); a beautiful green diopside from Tanzania; and less well-known species such as serandite from Quebec, inesite from South Africa and China and hedenbergite from Sweden.


The term phyllo comes from the Greek work for leaf.   Indeed, in this sub-family the tetrahedrons are organized in leaves, or sheets, for which the anionic group can be written as  Si4O10. It includes important minerals such as those from the mica, clay and serpentine groups.

This sub-family represents around 6.5% of mineral species.

Micas --more than 40 known species— are essential minerals in certain rocks.  Some of them, such as muscovite, can be found in abundance in well-formed crystals that can reach or exceed a meter in size and are often used in industry as insulators of heat or electricity.  Because of this, they are not very popular with collectors, which is a mistake because the truly beautiful specimens are quite rare.  Clays are in general composed of microscopic crystals, making them a poor choice for a collection focused on mineral esthetics.  The serpentine group is a vast family of minerals that make up the soft and often green rocks used for making

تنّور  type ovens or cheap sculptures. The leaves in this last family are not always flat: they can be undulating (like in sheet metal) or folded back like rods, in which case we get asbestos.  However, we do find rarer and much sought-after minerals in this family as well as other beautiful varieties like chrysocolla, cavansite and apophyllite.  

The collection possesses some exceptional examples of phyllosilicates.  One of the rarest is pyrosmalite from Sweden in perfectly hexagonal prisms.  In the realm of mineral esthetics, we should mention one of the best chrysocolla specimens from the Congo.  Apophyllites are very well represented with specimens from the rich deposits in India.  Green-colored samples are particularly popular, the most spectacular consisting of two balls of green crystal on a white gangue of stilbite.  A cavansite specimen in deep blue contrasting with white stilbite also comes from India.


The term tecto comes from the Greek word for structure or framework.  In this family all the SiO4 tetrahedrons are linked to one another by common oxygen bonds in such a way that they constitute a framework of tetrahedrons throughout the space.  A great many tectosilicates are also aluminosilicates, meaning that a more or less large part of the silicon atoms have been replace by aluminum atoms.  (We remember that aluminum is the third most common element in the Earth’s crust after oxygen and silicon, these three elements together making up 82% of the crust.)  Thus, we find in their chemical formula symbols of the type (Si,Al)O2.  As aluminum is a 3+ ion and silicon a 4+ ion, the imbalance in the charges is compensated for by other metal ions.  

This sub-family accounts for around 4% of mineral species.  It includes, among others, the feldspar, feldspathoid and zeolite groups.  Feldspars form a family of 16 species, some of which are the most important constituents of the principal magmatic rocks of the Earth’s crust, like granite and basalt for example.  Extremely abundant, feldspar crystals often take on a stony aspect that renders them less attractive.  In industry they constitute the raw material for making porcelain.  The feldspathoid family sets itself apart by a percentage of aluminum that is more elevated than in feldspar.  In this group we find some colorful minerals that are much sought-after such as lazurite (the main component in lapis lazuli), afghanite and sodalite.  Zeolites form a very large family with more than 80 species.  Their name comes from Greek for “stone that boils” because they lose their water of constitution when heated.  They are fragile minerals that form quite easily when a rock (often basaltic) is “washed” by hot water.  The great basaltic expanses like those in Iceland and the Deccan peninsula of India are rich in geodes covered in zeolite crystals.  In industry, natural or artificial zeolites are used as filters to purify and soften water, and as support for catalysts, etc., thanks to their internal structure.  As a general rule, the hardness of tectosilicates is mediocre and their density is relatively low.

The collection exhibits a representative sampling of feldspar:  transparent orthoclase from Madagascar, one of the best found; amazing amazonite (blue-colored microline) with smoky quartz from Colorado (USA); an enormous blue-green microline from Brazil; and hyalophane from Bosnia.  Feldspathoids are also represented by lazurite and afghanite from Afghanistan.  One can also discover minerals not belonging to the families cited above, such as some very handsome danburites from Mexico and an excellent helvite series from China.

Class 9 - Organics

Since the nineteenth century chemistry has distinguished substances of mineral origin, formed in nature under natural factors like water, pressure and temperature, etc., from substances of organic origin, that is formed by living beings.  The latter have chemical formulas that are much more complex and varied than those found in mineral chemistry. Thus one molecule of DNA contains hundreds of millions of atoms, while the chemical formulas for the most complex minerals never exceed a few hundred atoms.  And yet, organic molecules are only composed of atoms from a limited number of elements at the center of which we can always find carbon (the others are hydrogen, oxygen, sulfur, nitrogen and phosphorus).  

But it sometimes happens that rather simple organic molecules, under certain conditions and without the intervention of living beings, manage to form and to take on beautiful crystalline shapes.  These molecules make up the Class 9 of organic molecules, a sufficiently small group to merit their classification in general with the Class 5 carbonates, the other mineral class that contains carbon.  The collection only exhibits two such species: two examples of whewellite –whose molecule, by the way, is the main component in kidney stones in people— in the most beautiful specimen to have ever come out of Germany, and a handsome twinned crystal from Russia as well as mellite from Hungary.