14 Facts You Should Know About Minerals

14 Facts You Should Know About Minerals. Photos from the left to right. Tourmaline Majesty credit: Orbital Joe.|| Zoisite var. Tanzanite photo: mim museum.|| Elbaite with albite and Lepidolite.|| Rubellite Tourmaline, Quartz, MIca, Cleavelandite and Orthoclase. © DI (FH) Rudolf Watzl || Fluorite on sphalerite (Elmwood, TN, USA) || A slice of an amethyst by Rob Lavinsky|

1- A mineral is a naturally occurring substance, representable by a chemical formula, that is usually solid and inorganic, and has a crystal structure.

2- The exact definition of a mineral is under debate, especially with respect to the requirement a valid species be abiogenic, and to a lesser extent with regard to it having an ordered atomic structure.

Stunning Fluorite from Denton Mine, Cave-in-Rock, Hardin County, Illinois, USA Specimen Fine Mineral International, Credit James Elliott

3- There are over 5,300 known mineral species; over 5,070 of these have been approved by the International Mineralogical Association (IMA).
4-The silicate minerals compose over 90% of the Earth's crust. Silicon and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals.

5- Minerals can be described by various physical properties which relate to their chemical structure and composition. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, and specific gravity. More specific tests for minerals include magnetism, taste or smell, radioactivity and reaction to acid.  (How to Identify Minerals in 10 Steps (Photos))

Amazing Azurite found in Bisbee Arizona!

6- Non-silicate minerals are subdivided into several other classes by their dominant chemistry, which included native elements, sulfides, halides, oxides and hydroxides, carbonates and nitrates, borates, sulfates, phosphates, and organic compounds. The majority of non-silicate mineral species are extremely rare (constituting in total 8% of the Earth's crust), although some are relative common, such as calcite, pyrite, magnetite, and hematite.
7-The base of unit of a silicate mineral is the [SiO ₄] ⁴⁻ tetrahedron.  In the vast majority of cases, silicon is in four-fold or tetrahedral coordination with oxygen.

8-Minerals are not equivalent to rocks. A rock is either an aggregate of one or more minerals, or not composed of minerals at all. (The Difference Between Rocks and Minerals)

Chalcopyrite covering chalcocite from Daye mine, China. Specimen: Huanqiu Crystal Mineral Museum specimen, photo by John Veevaert

9-The abundance and diversity of minerals is controlled directly by their chemistry, in turn dependent on elemental abundances in the Earth.
10- The majority of minerals observed are derived from the Earth's crust.

11- Eight elements account for most of the key components of minerals, due to their abundance in the crust. These eight elements, summing to over 98% of the crust by weight, are, in order of decreasing abundance: oxygen, silicon, aluminium, iron, magnesium, calcium, sodium and potassium.

Wulfenite and mimetite - Ojuela Mine, Mapimí, Mun. de Mapimí, Durango, Mexico mw Credit: Montanpark

12- Differences in crystal structure and chemistry greatly influence other physical properties of the mineral. The carbon allotropes diamond and graphite have vastly different properties.

13- Three main groups of minerals are identified on the basis of the Property of color: idiochromatic, allochromatic, and pseudochro-matic.

• Idiochromatic minerals are "self colored" due to their composition. The color is a constant and predictable component of the mineral. Examples are blue Azurite, red Cinnabar, and green Malachite.
• Allochromatic minerals are "other colored" due to trace impurities in their composition or defects in their structure. In this case, the color is a variable and unpredictable property of the mineral. Examples are the blue in Amazonite (orthoclase), yellow in Heliodor (spodumene) and the rose in rose quartz.
• Pseudochromatic minerals are "false colored" due to tricks in light diffraction. In these cases, color is variable but a unique property of the mineral. Examples are the colors produced by precious opal and the shiller reflections of labradorite.