What Are Minerals? Minerals are materials that meet five requirements. They are: 1) naturally occurring, 2) inorganic, 3) solids, 4) with a definite chemical composition, and, 5) an ordered internal structure.

There are approximately 4000 different minerals, and each of those minerals has a unique set of physical properties. These include: color, streak , hardness , luster , diaphaneity, specific gravity, cleavage, fracture, magnetism, solubility, and many more.

Both minerals are crushed for use as a soil treatment, and in this purpose anhydrite is superior. One ton of anhydrite has more calcium than one ton of gypsum - because gypsum is about 21% water by weight.

Minerals: Information about ore minerals, gem materials and rock-forming minerals. Volcanoes: Articles about volcanoes, volcanic hazards and eruptions past and present. Gemstones: Colorful images and articles about diamonds and colored stones.

A small number of minerals and rocks will glow with spectacular colors under ultraviolet light. Learn how this happens.

Geology.com is one of the world's leading portals to geology and Earth science news and information for rocks, minerals, gemstones, energy, volcanoes, earthquakes, careers, geologic hazards, and more.

Minerals: Information about ore minerals, gem materials and rock-forming minerals. Volcanoes: Articles about volcanoes, volcanic hazards and eruptions past and present. Gemstones: Colorful images and articles about diamonds and colored stones.

Biotite is a name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks. These include annite, phlogopite , siderophyllite, fluorophlogopite, fluorannite, eastonite, and many others.

Minerals are "crystalline." In other words, they have an ordered atomic structure. In contrast, mineraloids are "amorphous." This means that their internal atomic structure is not ordered. Without the ordered atomic structure, mineraloids never produce well-formed crystals.

Calcite and other carbonate minerals have a low resistance to weathering and can be attacked by acids in natural waters and soils. When testing material that has been exposed at Earth's surface, it is very important to test unweathered material.