There are various mineral types and classifications. Widely used types of minerals are gems, ores, precious stones etc. However these “mineral types” lack solid definition and they are often mixture of various minerals with different chemical and physical properties. Scientists mostly use Strunz classification based in mineral chemistry and crystalography. Other very popular system is Dana classification based on structure.
Commonly used types of minerals
Minerals with certain economic value are called industrial minerals. Unlike ores these minerals are not limited only to metals. Many clay minerals like kaolinite or bentonite are used in construction industry, calcite is used in cement production, feldspar and quartz are major part of ceramics, zeolites are used in construction materials and chemical industry etc. Economically viable accumulations of these minerals are called mineral resources.
Minerals containing some metal are often labeled as ore minerals. The most common minerals in this group are various sulfides, oxides and native elements. Typical examples are pyrite, galena, sphalerite, magnetite, haematite, uraninite or native gold, silver and copper.
Gems and precious stones
There is no solid definition of precious stone or gem. Generally gems must be hard and usually translucent or clear. Classic gems like diamond, emerald, ruby or saphire are very hard, have no cleavage and gem grade material is clear and very expensive. On the other hand materials like jasper or agate are often just colorful hard stones produced in vast amount. Rarelly also soft minerals like aragonite, calcite or fluorite are used in jewellery.
Scientific Strunz classification of minerals
Native elements are minerals made of pure element or alloy. Elements are usually quite rare except graphite (carbon) and sulfur. Gold is present almost anywhere but in very low concentration. Other native metals like copper, silver, arsenic, bismuth, antimony or platinum are present only at certain ore deposits in small amounts. Well known example of non-metallic native element is cubic form of carbon – diamond. Very rare clear diamonds are valuable gems.
Many metals occur naturally in the form of sulfides. Most of sulfides are of magmatic or hydrothermal origin but some may be present also in sedimentary rocks. Typical examples are pyrite, pyrrhotite, chalcopyrite, galena, sphalerite, pentlandite, bornite and molybdenite. Sulfides are source of widely used metals like copper, lead or zinc. Rare metals like gold, silver or indium are often present in common sulfides in tiny amounts and are valuable side product.
After silicates oxides are the most abundant minerals on Earth. Oxide minerals are mixture of metals with oxygen or hydroxyl group. The most common is quartz which is important industrial mineral used in ceramics and electronics production. Varietes of quartz and chalcedony are gems like amethyst, smoky quartz, rose quartz, jasper or agate. Other gems are corundum (ruby and saphire) or spinel. Many oxides are important ores like haematite, magnetite, bauxite, cassiterite, pyrolusite, rutile and ilmenite.
Halides are usually mixture of alcalic metals with halogenide. Well know example is halite which is common table salt. Lot of salt is made directly from sea water but the other part comes from marine sediments called evaporites. Other widespread and important mineral is fluorite which is used in steel production. Fluorite is also the only industrial source of fluorine. Cryolite was used before in aluminum production but lack of natural deposits resulted in syntetic cryolite production from fluorite.
Common carbonates like calcite or dolomite are widespread and they form sedimentary rocks limestone or dolomite and are part of many other sedimentary rocks. Many limestone bodies contain caves because calcite is partially soluble in water. Other common carbonate is aragonite which is present in many organic shells and recent carbonate sediments. Many secondary carbonates forms by weathering of sulfides. These include popular malachite and azurite but also more rare hydrozincite, smithsonite or cerussite
The only common sulfates are gypsum, anhydrite and baryte. Gypsum and anhydrite are mined together with salt from evaporite deposits but most comes as byproduct from coal power plants. Anhydrite and gypsum are major part of drywalls, plaster slabs and many fine and hard plasters. Baryte is often present at ore veins, it is used in various industrial applications and as a source of baryum. Nice light blue crystals of celestite are source of strontium. Less common sulfates are usually products of sulfide weathering.
Most common phosphate is apatite. It is source of phosphorus and lot of sediments rich in apatite are used as a fertilizers. Phosphates monazite and xenotime are ores of rare earth elements (REE) like cerium or yttrium. Phosphates also include many minerals formed by weathering of metal ores these include erythrite, annabergite or vivianite. Also many secondary uranium minerals like autunite or torbernite are phosphates.
The most common minerals on earth are silicates. These are minerals forming most of rocks and they are important for many industrial applications. Common groups of silicates are pyroxenes, amphiboles, clays, feldspars, micas, tourmalines, zeolites or garnets. Silicates like topaz, emerald, colorful tourmalines, almandine and many others are highly priced gems. Feldspars, micas or zeolites are very important for production of ceramics, electronics, construction materials, chemicals and many other applications.