HISTORY, NAME, LOCALITIES: Although known since antiquity, calcite’s many confusing crystal habits precluded recognition as a species until 1845. Its name stems from the Greek chalx, meaning “lime.” Calcite is found worldwide; notable collecting localities are in England, Iceland, Germany, India, and the United States (Tennessee, Missouri, Michigan, New Jersey).
MINERALOGY, PROPERTIES, OCCURRENCE: Calcite [calcium carbonate, CaCO3], pronounced CHAL-site, is the most abundant carbonate mineral. It crystallizes in the hexagonal system (trigonal subsystem); crystals are usually rhombohedral, scalenohedral, or prismatic with a unusually wide variety of habits. It has a Mohs hardness of 3.0, perfect cleavage in three directions to form rhombohedrons, vitreous-to-dull luster, and a specific gravity of 2.7-3.0. It is usually white or colorless, but impurities create a wide range of pale colors. Calcite develops in many mineralogical environments, including pegmatites, carbonatites, chemical and sedimentary rocks, metamorphic rocks, and hydrothermal veins.
METAPHYSICAL PROPERTIES, LORE, USES: According to metaphysical practitioners, calcite enhances learning abilities, reduces fear and stress, removes negative energies, and promotes creativity and imagination. Calcite is the primary mineral component of limestone, which is mined in huge quantities for use as dimensional stone, in cement, and as a metallurgical flux; and marble, which serves as a dimensional stone and sculpting medium. Banded, massive forms of calcite, known as “marble onyx,” are fashioned into ornamental objects.
COLLECTORS’ INFORMATION: Calcite specimens are widely sought by collectors for their remarkable variety of crystal habits and colors, unusual size, affordability, excellent crystal development, and, in composite specimens, interesting associations with many other minerals.
QUARTZ (var. ROCK CRYSTAL)
HISTORY, NAME, LOCALITIES: Rock crystal, which is common and occurs worldwide, has been collected since prehistory. Notable collecting localities are found in India, Brazil, Germany, Peru, Bolivia, Namibia, Russia, and the United States (Arkansas, Colorado, Maine, Connecticut, Virginia).
MINERALOGY, PROPERTIES, OCCURRENCE: Rock crystal is the transparent, colorless variety of macrocrystalline quartz [silicon dioxide, SiO2). The word “quartz” is believed to have originated with the Slavic kwardy, meaning “hard,” in allusion to its substantial hardness. It crystallizes in the hexagonal system and occurs mainly in hydrothermal veins, granite pegmatites, and as geode linings as short-to-long, horizontally striated, hexagonal, prismatic crystals with pyramidal terminations and distinctive, water-clear transparency. It has a Mohs hardness of 7.0, a conchoidal fracture, vitreous luster, and specific gravity of 2.65.
METAPHYSICAL PROPERTIES, LORE, USES: Rock crystal has since antiquity been one of the most widely collected of all minerals. It has served as a gemstone and ornamental stone in many cultures. Until quartz was synthesized in the 1960s, rock crystal was vital to electronic frequency controls, filters, and timing devices. Modern metaphysical practitioners call rock crystal the “universal crystal” because of its numerous abilities to sharpen insight, enhance spiritual development, improve concentration, refine focus, and energize the mind.
COLLECTORS’ INFORMATION: Rock crystal is widely collected for its brilliant transparency, superb hexagonal crystal development, and frequent occurrence on large plates and in geodes to make interesting display pieces.