Chemical Mineralogy and Groups

Chemical Mineralogy and Groups

Elements. There are a few minerals that consist of single elements alone. For example, gold, Au.

Sulfides. A very important group of minerals consisting of combinations of the various metals with the element sulfur, are known as sulfides. They include the majority of the metallic ore minerals. For example, pyrite, FeS2.

Sulfo- salts. This group of minerals includes a series which mostly contain lead copper or silver in combination with sulfur and either antimony or arsenic. For example Tetrahedrite, Cu8Sb2S7.

Haloids. This group includes minerals that are salts of the halogen acids, chiefly hydrochloric or hydrofluoric acids. Examples are halite, NaCl , and fluorite, CaF2.

Oxides. The minerals of this group contain a metal in combination with oxygen. For example, hematite, fe2O3.

Hydroxides. An hydroxide is mineral that contains the hydroxyl group, OH, as an important radical. For example, limonite, Fe4O3(OH)6  .

Carbonates. The carbonates are salts of carbonic acid, H2 CO3. For example, calcite, CaC3.

Silicates. The silicates form the largest chemical group among minerals. They contain various elements as bases, the most common of which are sodium, potassium, calcium, magnesium, aluminium, and ferrous and ferric iron. They are frequently very complex in their chemical structure. They are salts of a number of different silicic acids, the most important of which are as follows:

• Orthosilicate acid = H4SiO4, which is represented by almandite, Fe3 Al2 (SiO4)3.
• Metasilicic acid = H4Si2O6 or H2SiO3, represented by leucite, KAI (SiO3)2.
• Polysilicic acid = H4Si3O8, represented by orthoclase, KAISi 3O8.

Niobates and Tantalates. These are combinations of various metals with the rare niobic and tantalic acids. For example, columbite De Nb2O6 and tantalite, FeTa2O6.

Phosphates. The sulfates are salts of some phosphoric acid. The most common member of the group is the mineral apatite, Ca4 (CaF) (PO4)3.

Sulfates. The sulfates are salts of sulfuric acid, H2SO4. For example, gypsum, CaSO4. 2H2O.

Tungstates. These are salts of the rare tungstic acid H2WO4. For example scheelite, CaWO4.