Minerals make up Earth’s rocks, soils and sands. They are found both on Earth’s surface and deep underground. Minerals are inorganic substances. And mineralogists are people who study the science of minerals, also known as mineralogy.
As rocks are subjected to heat and pressure, like getting buried deeper and deeper for example, they change. Different minerals appear in any given rock depending upon the type of rock and the amount of heat and pressure the rock undergoes. Geologists can look at the minerals in rocks to figure out how much heat and pressure the rock has undergone. Rocks are composed of one or more minerals and minerals are composed of one or more elements.
Adamite is a favorite among collectors of fluorescent minerals because of its consistent bright green fluorescence under short and long UV light. It also makes a wonderful mineral specimen in ordinary light. The typical lime green color of its adamantine (high luster) crystals set on top of its commonly associated red limonite matrix make specimens particularly attractive.
Aluminium or aluminum is a chemical element with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth’s crust; it is the third most abundant element after oxygen and silicon and the most abundant metal in the crust, though it is less common in the mantle below. The chief ore of aluminium is bauxite. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. Native aluminum rarely occurs naturally in its elemental form, even though only oxygen and silicon are more abundant in the earth’s crust. It has been found in volcanic muds and as tiny grains in highly unusual environments along with other elemental metals. Aluminum is known as aluminium outside of the United States.
Antimony is a chemical element with symbol Sb (from Latin: stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite. Antimony and Arsenic are almost identical. In many instances, the only way to tell them apart is by conducting complex scientific tests. Stibarsen, a mixture of arsenic and antimony, is also indistinguishable through common methods.
Arsenic is historically the poison of choice for many murders, in reality and in fiction. Here, arsenic is dealt with only as mineral specimens and is not to be ingested. Although it has been used as a poison, arsenic has many chemical uses and is quite an important element. Arsenic does not often form in its elemental state and is far more common in sulfides and sulfosalts such as arsenopyrite, orpiment, realgar, lollingite and tennantite. Due to the abundance of these arsenic bearing ores and the rarity of native arsenic, it is not an important ore of itself. Native arsenic is found in silver ore veins and is processed along with the silver ore and is therefore is a minor source of arsenic.
Azurite is a copper carbonate hydroxide mineral. It is best known for its characteristic deep blue to violet-blue color. The blue color, known as “azure,” is like the deep blue evening skies often seen above deserts and winter landscapes. Azurite is not a common or abundant mineral, but it is beautiful and its blue color attracts attention. It has been used by people in many parts of the world for thousands of years.
Barium Used as a heavy additive in oil-well-drilling mud, in the paper and rubber industries, as a filler or extender in cloth, ink, and plastics products, in radiography (“barium milkshake”), as getter (scavenger) alloys in vacuum tubes, deoxidizer for copper, lubricant for anode rotors in X-ray tubes, spark-plug alloys. Also used to make an expensive white pigment.
Bauxite is not a mineral, but rather a group of aluminum oxides. The term is generally used to describe the economically important mixture of these minerals, which form a mass of the individually classified members of Gibbsite, Boehmite, and Diaspore. Bauxite does not make aesthetic or interesting specimens as far as collectors are concerned, but it holds importance as being the primary ore of the metal aluminum.
Beryllos Named for the Greek beryllos, now meaning “beryl,” but previously used in reference to antiquated blue-green stones which may or may not have been Beryl. Beryl is a common mineral that occurs in granite, granite pegmatites, nepheline syenite, mafic metamorphic rocks, hydrothermal veins, and in vugs in rhyolite.
Coal is a sedimentary rock of biochemical origin. It forms from accumulations of organic matter, likely along the edges of shallow seas and lakes or rivers. Flat swampy areas that are episodically flooded are the best candidates for coal formation. During non-flooding periods of time, thick accumulations of dead plant material pile up. As the water levels rise, the organic debris is covered by water, sand and soils. Coal burns well, since it is mostly made of carbon. It has been mined for a long time for this reason. The industrial revolution started in Britain when people discovered how to smelt iron efficiently, and for this you needed coal. Britain has a lot of coal and iron, although many mines are no longer in use. There are different types of coal. Anthracite is a good quality coal which burns nearly without smoke or flame as it is nearly pure carbon. It is very shiny and hard.
Chromite is an oxide mineral composed of chromium, iron, and oxygen. It is dark gray to black in color with a metallic to submetallic luster and a high specific gravity. It occurs in basic and ultrabasic igneous rocks and in the metamorphic and sedimentary rocks that are produced when chromite-bearing rocks are altered by heat or weathering. Chromite is important because it is the only economic ore of chromium, an essential element for a wide variety of metal, chemical, and manufactured products. Chromite bricks are used to line blast furnaces, as they can resist extremely high temperatures.
Cobalt has yet to be found in nature, but is being grown in labratories and these cobalt specimens are starting to appear in rock shops. Since it has never been found in nature it is technically not a mineral although lab grown specimens can look like a natural stone. The element cobalt has many industrial uses especially in dyes and in magnets. As a dye, cobalt produces a spectacular blue color that is used most noteably in glass and ceramics. When alloyed with iron and nickel, cobalt produces a strong magnet. Cobalt has many uses in certain alloys for airplane parts and engines.
Copper is an element and a mineral. It is found in the oxidized zones of copper deposits; in hydrothermal veins; in the cavities of basalt that have been in contact with hydrothermal solutions; and as pore fillings and replacements in conglomerates that have been in contact with hydrothermal solutions. It is rarely found in large quantities, thus it is seldom the primary target of a mining operation. Most copper produced is extracted from sulfide deposits. Copper is one of only two coloured metals (the other is gold). It is usually a reddish brown colour but it turns green when it’s exposed to air for a really long time (think of the green colour as a form of rust).
Diamond is a rare, naturally-occurring mineral composed of carbon. Each carbon atom in a diamond is surrounded by four other carbon atoms and connected to them by strong covalent bonds – the strongest type of chemical bond. This simple, uniform, tightly-bonded arrangement yields one of the most durable and versatile substances known. Diamond is the hardest known natural substance. It is also chemically resistant and has the highest thermal conductivity of any natural material. Diamonds are really the size of grains of sand! Diamonds are just carbon, exactly the same element in graphite, which you find in pencil leads. The black mark that charcoal makes is carbon. However, in diamonds, the atoms are locked together into an incredibly strong structure. Diamond is by far the hardest natural material. In fact, it is harder than any man-made material. It is used industrially for cutting.
Feldspars are a group of minerals that have similar characteristics due to a similar structure. The feldspar group is a fairly large group with nearly 20 members recognized, but only nine are well known and common. Those few, however, make up the greatest percentage of minerals found in the Earth’s crust. The name “feldspar” comes from “field stone”, because when feldspar weathers, it releases large amounts of plant nutrients, such as potassium, which enrich the soil. Feldspars have particularly interesting effects with light. Moonstone seems to glow. Sunstone sparkles with reflected light.
Gold is an element and a mineral. It is highly prized by people because of its attractive color, resistance to tarnish, and its many special properties – some of which are unique to gold. Its rarity, usefulness, and desirability make it command a high price. Trace amounts of gold are found almost everywhere, but large deposits are found in only a few locations. A few of the minerals that bear gold in their respective formulas are in a subclass of sulfides called the tellurides. The element gold seems to have an affinity for tellurium and this is one of the only elements that gold can bond with easily. In fact only a few rare tellurides are found without gold.
Graphite is a mineral composed exclusively of the element carbon. Graphite has the same chemical composition as Diamond, which is also pure carbon, but the molecular structure of Graphite and Diamond is entirely different. This causes almost opposite characteristics in their physical properties. Graphite is very soft. It is used in the “lead” of pencils, which contain no lead at all, but are made of graphite and clay. Strangely enough, graphite has exactly the same chemical formula as diamond, the hardest substance known to mankind. They are both carbon. In diamond, the atoms of carbon lock together into an incredibly strong structure. In graphite, the atoms are arranged in a different way, in layers. This means that one layer can be rubbed off quite easily, which is what happens when you write with a pencil.
Gypsum forms deep under water when creatures like clams, oysters, scallops and other shellfish die. Their remains settle to the ocean floor in layers. Over time, hundreds of layers form and push down from on top of the original layer. This causes it to be turned into rock. Some of this rock contains gypsum. Gypsum is a very soft mineral.
Halite is the mineral name for the substance that everyone knows as “salt.” Its chemical name is sodium chloride, and a rock composed primarily of halite is known as “rock salt.” It can easily be distinguished by its taste. Since taste is an important property of salt, there is a right way to taste a specimen of halite (or an unknown mineral that is similar to halite) and a wrong way.
Iron is quite often a misnomer as natural iron is not necessarily “native” to Earth since it rarely occurs on the Earth’s surface by terrestrial processes. It is mostly found in the form of meteorites that have impacted the Earth’s surface.
Jade is a name that was applied to ornamental stones that were being brought to Europe from China and Central America. It wasn’t until 1863 that it was realized that the name “Jade” was being applied to two different minerals. The two minerals are both exquisite for the purposes that jade is put to task and are hard to distinguish from each other. There are two different minerals that are called Jade – Jadeite and Nephrite. Many specimens are just sold as Jade. The derivations refer to the belief that jade would cure pains in the side.
Kaolinite is a clay mineral, part of the group of industrial minerals. It is a layered silicate mineral, with one tetrahedral sheet of silica linked through oxygen atoms to one octahedral sheet of alumina octahedra. Kaolinite, which is named for its type locality, Kao-Ling, Jianxi, China; is a common phyllosilicate mineral. It lends it name to the Kaolinite Group, members of which also belong to the larger general group known as the Clays.
Lead is a common element, but is very rare in a native state. Some locations contain lead as a by-product of smelting operations, where masses of lead are formed, but they are not naturally occurring. Such specimens are occasionally sold to collectors. The U.S. is the world’s largest producer and consumer of refined lead metal.
Limestone is a very common sedimentary rock of biochemical origin. It is composed mostly of the mineral calcite. Sometimes it is almost pure calcite, but most limestones are filled with lots of other minerals and sand and they are called dirty limestones. Limestone is a grey rock. It is used as building stone, and to make concrete.
Lazulite is an aesthetic blue mineral that forms in distinct crystals. Its name is very similar and often confused with Lazurite, which is an entirely different mineral species. However, the names of both these minerals are derived from the term “Lazaward”, which means heaven in Arabic, alluding to their blue color.
Lithium compounds are used in ceramics and glass, in primary aluminum production, in the manufacture of lubricants and greases, rocket propellants, vitamin A synthesis, silver solders, underwater buoyancy devices, batteries.
Manganese is used to make alloy steels. Steel is mostly iron, but has other metals such as Manganese is in it. The most common form of Magnesite is white, microcrystalline, porous masses that are dull in luster, and have the appearance of unglazed porcelain. Because they are porous, they adhere to the tongue when licked.
Mercury is unique, as it is the only metal that is liquid at room temperature, having a melting point of -40 C, and a boiling point of 357 C. This silvery liquid metal is very dense, yet has a high surface tension that causes is to form tiny little perfect spheres in the pores of the rocks it is found in.
Mica is an important group of minerals. They represent the classic phyllosilicate mineral and are usually the first minerals to be thought of from this subclass of the Silicates Class. Micas are significant rock forming minerals being found in all three rock types: igneous, metamorphic and sedimentary.
Molybdenite is the most prevalent molybdenum-bearing mineral, and is named after that element. Prior to the discovery of molybdenum as a separate element in 1778 by Karl Wilhelm Scheele, Molybdenite was thought to be Graphite or a lead ore. In fact, the word molybdos means “lead” in ancient Greek. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum atoms sandwiched between sheets of sulfur atoms.
Moonstone is an orthoclase feldspar. “Othoclase” means “straight cleavage”. Oligoclase is not a well-known mineral but has been used as a semi-precious stone under the names of sunstone and moonstone. Sunstone has flashes of reddish color caused by inclusions of hematite. Moonstone shows a glowing shimmer similar to labradorescence, but lacking in color.
Nickel is extremely rare in nature, as it is almost always alloyed with iron. Iron meteorites, for example, are typically 6% to 20% nickel. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile. Pure nickel, powdered to maximize the reactive surface area, shows a significant chemical activity, but larger pieces are slow to react with air under standard conditions because an oxide layer forms on the surface and prevents further corrosion (passivation).
Pezzottaite is a mineral that is very similar to Beryl, but it contains lithium as well as the rare element cesium replacing some beryllium in its chemical structure. It is therefore scientifically classified as a separate mineral species from Beryl. When first found, it was though to be a variety of Beryl, but it wasn’t until 2003 that the IMA regarded Pezzottaite as a unique mineral species. It is named after Italian geologist Dr. Federico Pezzotta of Milan.
Platinum Group Metals (includes platinum, palladium, rhodium, iridium, osmium, and ruthenium): They commonly occur together in nature and are among the most scarce of the metallic elements. Platinum is used principally as catalysts for the control of automobile and industrial plant emissions, as catalysts to produce acids, organic chemicals, and pharmaceuticals. PGMs are used in bushings for making glass fibers used in fiber-reinforced plastic and other advanced materials, in electrical contacts, in capacitors, in conductive and resistive films used in electronic circuits, in dental alloys used for making crowns and bridges, in jewelry. Russia and South Africa have nearly all the world’s reserves.
Pyrite is also known as “Fool’s Gold”. It is a very pretty mineral and usually forms interesting crystals. The word “Pyrite” comes from the Greek words pyrites lithos, meaning “stone which strikes fire”. They discovered that when you hit pyrite with iron it would spark. This is why it was used to start fires.
Quartz is a chemical compound consisting of one part silicon and two parts oxygen. It is silicon dioxide (SiO2). It is the most abundant mineral found at Earth’s surface, and its unique properties make it one of the most useful natural substances.
Rare Earth Elements Industrial consumption of rare earth ores is primarily in petroleum fluid cracking catalysts, metallurgical additives, ceramics and polishing compounds, permanent magnets, and phosphors. Rare earth elements are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
Ruby is the red variety of corundum, the second hardest natural mineral known to antiquity. The non-red variety of corundum is Sapphire. Sapphires are well known among the general public as being blue, but can be nearly any color. The red color in ruby is caused by trace amounts of the element chromium. The best shade of red for ruby is often given the name “pigeon blood red”, but ruby can be any shade of red up to almost pink.
Sodalite is a lovely blue mineral, and it’s quite common. It is sometimes used as a substitute for Lapis Lazuli in jewelry, although good Lapis Lazuli is a much richer blue. Sodalite is a scarce mineral that can be rock forming. Sodalite is named in reference to its sodium content. It is used for carvings and some jewelry pieces. Its light to dark pure blue color is well known in the semi-precious stone trade. Sodalite is a member of the feldspathoid group of minerals. Minerals whose chemistries are close to that of the alkali feldspars but are poor in silica content, are called feldspathoids.
Sulfur is a chemical element with an atomic number of 16 and an atomic symbol of S. At room temperature it is a yellow crystalline solid. Even though it is insoluble in water, it is one of the most versatile elements at forming compounds. Sulfur reacts and forms compounds with all elements except gold, iodine, iridium, nitrogen, platinum, tellurium, and the inert gases. Pure Sulfur is bright yellow. The color may be altered if impurities are present. Clay and selenium impurities, as well as volcanic mixtures in sulfur can cause it to be slightly red, green, brown, or gray. Sulfur often occurs in petroleum deposits, where it is found coated with greasy black petroleum.
Silicon is rarely found in nature in its uncombined form. In fact it is amazing how rare native silicon is with 25.7% of the Earth’s crust being silicon. Silicon, binds strongly with oxygen and is nearly always found as silicon dioxide, quartz, or as a silicate. Silicon has been found as a native mineral only in volcanic exhalations and as tiny inclusions in gold.
Silver is a precious metal. It is used for jewelry, but it tends to tarnish. It was used for cutlery and tea-pots, and often handed down as heirlooms. “Selling the family silver” means squandering property held in trust for the future. Silver has an electrical and thermal conductance that is higher than any other metal. It has a higher reflectivity at most temperatures than any other metal. It has an attractive color and luster that resist tarnish and make the metal desirable in jewelry, coins, tableware, and many other objects.
Tantalite is the most widespread tantalum mineral and makes for an important ore of the industrially useful metal. Tantalum is used in alloys for strength and higher melting points, in glass to increase the index of refraction, and in surgical steel, as it is non-reactive and non-irritating to body tissues. Tantalite forms a series with the mineral columbite. In fact the two are often grouped together as a semi-singular mineral called columbite-tantalite in many mineral guides.
Titanium is a chemical element with symbol Ti and atomic number 22. It is a lustrous transition metal with a silver color, low density, and high strength. Titanium is resistant to corrosion in sea water, aqua regia, and chlorine. The element occurs within a number of mineral deposits, principally rutile and ilmenite, which are widely distributed in the Earth’s crust and lithosphere, and it is found in almost all living things, water bodies, rocks, and soils. The metal is extracted from its principal mineral ores by the Kroll and Hunter processes. The most common compound, titanium dioxide, is a popular photocatalyst and is used in the manufacture of white pigments.
Tungsten is used in metalworking, construction and electrical machinery and equipment, in transportation equipment, as filament in lightbulbs, as a carbide in drilling equipment, in heat and radiation shielding, textile dyes, enamels, paints, and for coloring glass. Major producers are China, Korea, and Russia. Large reserves are also found in the U.S., Bolivia, Canada, and Germany.
Turquoise is a valuable mineral and is possibly the most valuable, non-transparent, non-metal mineral in the jewelry trade. It has been mined for eons since at least 6000 BC. by early Egyptians. Its history also includes beautiful ornamental creations by Native Americans and Persians. Its popularity is still quite strong today. Turquoise is an antique ornamental stone, highly regarded for its unique and striking namesake color. Valued in both the ancient Persian and Native American civilizations, it still retains its popularity today. Turquoise specimens are often polished or sliced for collectors, and may even be dyed. Turquoise is porous and has a naturally waxy luster; it is sometimes impregnated with a plastic lubricant for to enhance its luster and increase its stability. Many Turquoise fakes exist. The most prevalent is white Howlite dyed blue to resemble Turquoise.
Vanadium is a chemical element with symbol V and atomic number 23. It is a hard, silvery grey, ductile, and malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) stabilizes the free metal somewhat against further oxidation. A compound of Vanadium is also an important catalyst in the manufacture of sulphuric acid. A catalyst is a chemical which helps a chemical reaction to happen, without being changed itself by the reaction.
Zeolites are a popular group of minerals for collectors and an important group of minerals for industrial and other purposes. They combine rarity, beauty, complexity and unique crystal habits. Typically forming in the cavities (or vesicles) of volcanic rocks, zeolites are the result of very low grade metamorphism. Some form from just subtle amounts of heat and pressure and can just barely be called metamorphic while others are found in obviously metamorphic regimes. Zeolite crystals have been grown on board the space shuttle and are undergoing extensive research into their formation and unique properties.
Zoisite and clinozoisite are minerals that form during the regional metamorphism and hydrothermal alteration of igneous, metamorphic, and sedimentary rocks. In those environments they are found in massive form and as prismatic crystals in veins that cut schists and marbles. They are also found as crystals in pegmatites that form on the margins of igneous bodies.
Zincite is an ore of zinc. Zinc combined with copper makes brass. Zinc is also used in batteries and is a rare mineral. Native zinc has been found in several locations but is never found in any abundance. It would be wrong to consider it an ore of zinc. First of all, an ore should be less valuable than its constituent metal. And since zinc is so rare in its native form, this is not true. Secondly, an ore needs to be common enough and exploitable enough to be profitable enough to mine.
Zircon is a zirconium silicate mineral with a chemical composition of ZrSiO4. It is common throughout the world as a minor constituent of igneous, metamorphic, and sedimentary rocks. Zircon is a popular gemstone that has been used for nearly 2000 years. It occurs in a wide range of colors and has a brightness and fire that rivals those of diamond. It is a crystal, transparent to nearly opaque, which is usually reddish brown, but can be other colours including transparent. It is the brown form which is called hyacinth.