4,000 naturally occurring minerals—inorganic solids that have a characteristic chemical composition and specific crystal structure have been found on Earth. They are formed of simple molecules or individual elements arranged in repeating chains, sheets, or three-dimensional arrays.
Normally Minerals are typically formed when molten rock, or magma, cools, or by separating out of mineral-rich water, such as that in underground caverns. In general, mineral particles are small, having formed within confined areas such as lava flows or between grains of sediments. Large crystals found in geodes and other rocks are relatively rare.
Are all gems real minerals? A mineral is an inorganic, naturally occurring substance with distinct chemistry and crystalline structure. Gemstones are materials that have an economic or aesthetic value. Therefore, not all gemstones are minerals. For example, amber is solidified tree resin, so it is not a mineral.
- What are Organic Gems?
- Although most gemstones are mineral materials, a number of organic materials are also considered to be gemstones. The most common of these are pearl, bone, amber, coral, jet, and ivory. These are materials, produced by organisms, that have been cut into gem sand other ornamental objects.There are also organic materials that have been mineralized (replaced and infilled by chalcedony, opal, calcite, aragonite, pyrite, or other mineral material). Although the material itself is not organic, it does preserve an organic structure. Examples include petrified wood fossil coral, dinosaur bone, and other fossilized organisms or parts of organisms.
Sapphire, like ruby, is made of corundum (Al2O3) and has a hardness of 9. However, instead of Cr impurities, the crystal contains iron and titanium
|Mohs’ HARDNESS SCALE|
Many minerals form beautiful crystals, but the most prized of all are gemstones. Uncut gems often look fairly ordinary–like rocks. It’s only when they are cut and polished that they obtain the brilliance and luster that gives them their value.
Historically, gems have been divided into precious and semiprecious classes. There are a number of semiprecious gems, many quite beautiful, but diamonds, rubies, sapphires, and emeralds continue to qualify as “precious.” (At one time, amethyst was also considered a precious gem,