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Native Elements
Native elements exist free and uncombined, meaning they are not a compound with any other element. Natural pockets of gold, silver, copper, platinum and iron characterize this group. These members display a metallic luster and jagged, uneven fracture. These soft, malleable, ductile minerals conduct heat and electricity and have low melting points. Non-metallic members include sulfur, diamonds and graphite.
Sulfides and Sulfosalts
These heavy minerals look metallic and are associated with other metallic minerals in ore veins. Some have distinctive colors and are soft. Except for molybdenite, they'll shatter when hit with a hammer. Other members of this group include bornite, galena and pyrite.
Oxides and Hydroxides
These hard, heavy minerals occur in igneous, volcanic and metamorphic rocks as well as ore veins and hydrothermal solutions. Oxides resist weathering and vary in appearance. Those of economic importance are mined for iron, chromium, copper, zinc, manganese, tin and uranium.
Halides
The halide minerals contain chlorine, bromine, fluorine or iodine. They're light in color, water-soluble and soft. Many of them, like table salt, form cube-shaped crystals.
Carbonates
These easily decomposed minerals differ from others because of their effervescence when dissolved in acid. They can be chalky, colorful or twinned. Examples include calcite, dolomite, malachite and azurite.
Nitrates and Borates
The high-solubility and soft nature of nitrates and borates restricts these minerals to mostly dry climates. Borates, such as borax, form in sheets or chains.
Sulfates
These soft, translucent minerals occur with commercial ores or scattered throughout limestone. They also form in hydrothermal veins and vary between water soluble and highly insoluble. Members include barite, gypsum and anhydrite.
Phosphates, Vanadates and Arsenates
These uncommon soft minerals occur in many ways. Their colorful crystals can be scattered throughout granites, gneisses and pegmatite, or they can form as alteration products from the effects of weathering on other minerals. They exist near lead and zinc minerals or as thin crusts. Elements found in these minerals include vanadium, lithium and uranium. Turquoise belongs to the phosphate group.
Tungstates, Molybdates and Uranates
Each of these soft, heavy, colorful minerals forms in near-surface ores or as products of weathering of other minerals. They can also be found in pegmatite and high-temperature quartz veins of granitic rocks. Their distinctive appearance makes them easily recognizable. Tungstates are the primary source for tungsten.
Silicates
The internal structure of silicates varies among ring structures, tetrahedrons, sheets, chains and double chains. Even though they are the most common group of minerals, their properties vary greatly, making them harder to identify. Common silicates include garnet, zircon, topaz, talc, quartz, opal, the mica and the zeolites.