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).

Calcite is one of the most important carbonate minerals. It is often referred to as a industrial mineral, and is found in over 300 forms. The photo is from the Southern California Deserts, is white. Calcite may be any color, from colorless to black, depending upon the other minerals contained in it. Calcite has a hardness of 3, SG of 2.72, and has a rhombohedral cleavage. Calcite is used in cement making, aggregate, quick lime manufacture, metallurgical uses and for a number of other industrial uses. 
Limestone is a sedimentary rock, is comprised primarily of the mineral calcite (CaCO3). Limestone is predominately calcium carbonate, with minor amounts of magnesium carbonate, silica, clay, iron oxide, or carbonaceous material. Limestone is widely distributed, may be fine grained, compact, coarse grained, or composed of fragmented material. Limestones comprise approximately 10 percent of the sedimentary rocks.

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It forms either by direct crystallization from water (usually seawater) or by accumulation of shell and shell fragments. Most limestones were formed by organisms such as corals, mollusks, brachiopods, etc. In the first case, it carries a record of the chemical composition of seawater and it provides evidence of how that composition has changed with time. In the second case, limestone provides a record of the evolution of many important fossils. Limestone usually forms in shallow water less than 20 m (70 ft) deep and thus also provides important geological information on the variation in sea level in the past. Limestone rocks are frequently riddled with caves. All limestone forms from the precipitation of calcium carbonate from water. Calcium carbonate leaves solutions in many ways and each way produces a different kind of limestone. All the different ways can be classified into two major groups: either with or without the aid of a living organism.

White limestone is relatively rare, and has many commercial uses, fillers for paint, rubber products, putty, pottery, paper manufacturing, plastics, food, flooring, PVC Pipes, white ink, tooth paste, wire coating, caulking, glue, caulking compounds, resins, polyester, ceiling and wall textures, dry wall, mud, joint compounds, stucco, fiberglass, roofing shingles, and a few more.
The white limestone specimen was provided by Specialty Minerals, Lucerne Valley CA mine.