Chemical properties of gemstones.
Gems, like all minerals, have a specific chemical composition. The elements occurring in them are generally common elements, which are common components of minerals.
The most common element is oxygen O. Except for the diamond, which is pure carbon, all gemstones contain oxygen as an essential ingredient. The second most common element is silicon Si. It combines with oxygen in relation to 1:2, forming silicon dioxide, i.e. SiO2 silica.
The most common element after silicon is aluminum (aluminium Al). Combined with oxygen, it forms aluminum oxide Al2O3. Aluminum oxide is the mineral corundum and its varieties - ruby and sapphire. Aluminum is also found in many silicates. Aluminum silicates are topaz, sillimanit, Andalusian, cyanite. This element is also an important component of aluminosilicates.
The next element in quantity in the earth's crust is iron Fe. Therefore, that this element may be two- or trivalent, it forms two different oxides: Fe + O - ferrous oxide - and Fe2 + O3 - ferric oxide (hematyt). The nature of the mixed oxide is magnetite Fe3O4, in which there is both, and trivalent. Both iron oxides are involved in the construction of many silicates and aluminosilicates. It is worth adding here, that the presence of iron clearly affects the color of the chemical compound. Divalent iron causes a bluish color, greenish and black, on the other hand, trivalent iron gives reddish colors, yellowish and brown. Therefore, weathered rocks on the ground, which almost always contain iron, are yellowish-brown in color. For example, bluish diamond bearing blue ground rock (heavenly earth) it turns into a weathered, yellowish-brown rock on the ground, zwaną yellow ground (yellow earth).
Further elements are calcium Ca and magnesium Mg, being the main components of common minerals: kalcytu, dolomite, piroksenów, amfiboli oraz oliwinu (chrysolite).
Of the alkali metals, potassium K and sodium Na are the most common. They are primarily feldspar. Sodium silicate is lapis lazuli. Belonging to the alkali metals, lithium is found in kunzite and hidden.
In its native form, it occurs in nature only approx 20 elements, e.g.. sulfur, gold, silver, copper, platinum, carbon. The vast majority of elements are found in a variety of chemical compounds, mainly in the salts of oxygen acids, among which silicates are the most numerous. Precious stones belong to different classes of minerals in terms of their chemical composition.
The most precious gemstone - diamond - is an element, The iron sulfides are pyrite and marcasite, zinc sulfide is sphalerite. The halides include fluorspar, which is calcium fluoride. Silicon oxide is quartz classified as silicates on the basis of its internal structure. Precious gemstones - rubies and sapphires - are colored varieties of corundum, which is alumina. The iron oxide is hematite, titanium - rutile, tin - cassiterite, zinc - zincite. Complex oxides containing more than one cation are spinel - magnesium and aluminum oxide, chrysoberyl - aluminum and beryllium oxide, chromite - iron and chromium oxide.
Carbonates include the common calcite and its ara-gonite variety, being calcium carbonates, azurite and malachite are copper carbonates, rhodochrosite is manganese carbonate, smitsonite - zinc. The hydrated calcium sulphate is gypsum and its fine crystalline variety - alabaster; phosphates are: apatite - calcium phosphate, turquoise - aluminum and copper, beryllium - sodium and beryllium, brazilianite - sodium and aluminum, lazulite - iron, magnesium and aluminum, varisite - of aluminum.
Most gemstones are silicates. The main components of silicates are elements: oxygen, silicon, glin, iron, calcium, magnesium, sodium and potassium. They also contain lithium, beryl, bar, mangan, as well as additional anions, e.g.. F-, Cl-, [SO4]2-. Water is also often present in the silicates, sometimes hydrogen. Some silicates contain several elements and the chemical formulas of these minerals are sometimes very complicated. For this reason, the chemical formula of the same mineral is sometimes presented differently by different authors.
In the past, silicates were considered as salts of various hypothetical silicic acids, like orthosilicic acid, metasilicic acid, etc.. Currently, silicates are classified according to their internal structure, depending on the way of mutual connection of silica anions [SiO]4-, being essential elements of their structure. Silicates, in which some of the Si4 + silicon ions in the silica anions are replaced by aluminum Al3 + ions are called aluminosilicates.
Silicates and aluminosilicates are divided into island ones, group, annular, chainsaw, ribbon, layered and spatial. Sometimes borane silicates, boron silicates and beryllium silicates are separated into separate groups. Island silicates include precious stones such as olivines, grenades, zirconium, sillimanit, Andalusian, dysten, topaz, staurolit, tytanit. Epidote and Vesuvian are group silicates, cyclic silicates include dioptase and cordierite, for chain silicates - wollastonite, Rodon, pyroxenes and their jade. Ribbon silicates are amphiboles, prehnit, actinolite, tremolit, nephrite, layered silicates - chrysocolla, serpentyn, sepiolit. The spatial silicates include quartz and its varieties: cryptocrystalline chalcedony and amorphous, opal water, as well as feldspars, sodality haüyn, lazuryt, skapolit. Beryllium silicates are phenakite and beryllium, whose colorful varieties (emerald, akwamaryn i in.) are among the most valuable gemstones. The boranosilicates are tourmalines, dumortieryt, aksynit, datolit, cornerupin, danburyt.