THE GOLD OF THAT LAND: Biblical Minerals & Rocks  


 

51.     quartz 

See also "Agate," "Amethyst," "Carnelian," "Chalcedony," "Chrysoprase," "Crystal," "Flint," "Jasper," "Onyx," "Prase," "Sard," and "Sardonyx."

Mineralogy: Quartz occurs naturally in a bewildering array of varieties that acquired their own names early in antiquity, especially when used as gems. Quartz forms prismatic hexagonal crystals that terminate in rhombohedral faces in many combinations, often with horizontal striations. Quartz crystals commonly occur in intergrown, twinned masses.

    The distinctively colored varieties of coarsely crystalline quartz have their own names, such as amethyst, bull quartz, cairngorm, cat's-eye, citrine, rose quartz, and smoky quartz. Rutilated quartz contains fine needles of rutile, and aventurine has lustrous inclusions of shiny mica or hematite scales. Star quartz crystals have inclusions of rutile perpendicular to their long axis, and a well cut crystal displays them as starry rays of light.

    Cryptocrystalline varieties of quartz are even more diverse in color and habit. They were deposited from aqueous solutions in nodules or layers as silica gel or in an amorphous or opaline form, and they have since recrystallized as fibrous or microgranular quartz. The fibrous varieties have a vitreous luster and greasy feel, and are collectively known as chalcedony. Microgranular varieties are more opaque than chalcedony, and they have a duller or porcellanous luster and granular feel.

    Sources:

Dennen, William H., and Anita M. Puckett, 1971. On the chemistry and color of Rose Quartz. Mineralogical Record: 2-5, 226-227.

Frazier, op. cit.; 75-89.

Hurlbut, 1952, op. cit.; 319-321.

Lucas & Harris, op. cit., 402-403.

Ralph, Jolyon, 1993-2004. http://www.mindat.org/min-3337.html

Schumann, op. cit.; 116-153.


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