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).

Celestite is a Stronium mineral, is orthorhombic, has tabular or prismatic crystals, has a Mhos hardness of 3 to 3.5 and a SG of 3.9 to 4. It has a vitreous to pearly luster, is white, yellow, has a blue tinge, or occasionally green or reddish. The sample in the photo is from Lime City, Ohio (USA). Celestite is soluable in water. It is often associated with sulphur, gypsum, halite, aragonite, sphalerite and galena. It occurrs in two primary types, either disseminated as crystals (as the specemin in the photo), or in cracks and cavaties of sedimentary rocks. The crystal variety is typically found in shales, limestones and dolomites.

From the USGS

"Strontium commonly occurs in nature, averaging 0.034% of all igneous rock; only two minerals, celestite (strontium sulfate) and strontianite (strontium carbonate), however, contain strontium in sufficient quantities to make its recovery practical. Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development."

Some uses for stronium are glass, ceramics crt and flat panel display glass, paint addative,metallurgy, magnets and pyrotechnics, as stronium has a bright red flame.