A mineral is a naturally occuring, homogeneous, solid with a crystalline atomic structure. Crystallinity implies that a mineral has a definite and limited range of composition, and that the composition is expressible as a chemical formula. Some definitions of minerals give them as inorganic materials, however both diamonds and graphite are considered minerals, and both are primarily comprised of carbon, which would make them organic. So this leads me, as an engineer, to believe that mineralogists do not have a good, precise definition of a mineral, but rather a loose definition. The definition above, is the most inclusive and would include all substances currently described as minerals. The key items that make something a mineral are occurring naturally, and the definite crystal structure, that is expressible as a chemical formula. Rocks that do not meet this criteria are referred to as amorphis - not having a definite structure or expressible as a chemical formula. Some elements that occur naturally and are minerals are arsenic, bismuth, platinum, gold, silver, copper, and sulphur.

THE DEFINITION OF ORGANIC: Organic chemistry is the study of those substances containing carbon in combination with hydrogen (H), and a few other non metals, namely oxygen (O), nitrogen (N), sulfur (S) and the halogens (F2, Cl2, Br2, and I2).

Talc is a magnesium mineral, commonly found in metamorphic rocks, such as chlorite schists, serpentine and magnesite. It is monoclinic, crystals are tabular, has a hardness from 1 to 2.5, SG of 2.6 to 2.8, is generally green, white or gray in color. It can also be yellowish or reddish brown.

There are several types of talc, , Foliated Talc (hardness of 1, soapy or greasy feel), Stealite or Soapstone (massive, generally inpure, hardness of 1.5 to 2.5, gray to greenish in color and occurs in large deposits)and French Chalk (soft compact white masses.used as chalk in clothing industry for marking fabrics). The talc in the photo is soapstone.

Talc is used commercially because of its fragrance retention, luster, purity, softness, and whiteness. Other commercially important properties of talc are its chemical inertness, high dielectric strength, high thermal conductivity, low electrical conductivity, and oil and grease adsorption. Major markets for talc are ceramics, paint, paper, and plastics. **

** Uses of talc from USGS