GYPSUM (var. SELENITE)

HISTORY, NAME, LOCALITIES: Gypsum, pronounced JIP-sum, is hydrous calcium sulfate.  Its name stems from the Greek gypsos, or “plaster,” alluding to one of its early uses.  Selenite, pronounced SELL-en-ite, is the crystalline variety of gypsum.  Its name is derived from the Greek selénités, literally “stone of the moon” (from seléné, or “moon”), referring to the moon-like, pearly luster of its cleavage surfaces.  Collecting localities are found in Canada, Peru, Mexico, Spain, and the United States (Oklahoma, Utah, New York, Tennessee, and Nevada).

MINERALOGY, PROPERTIES, OCCURRENCE: The selenite variety of gypsum [hydrous calcium sulfate, CaSO₄·2H₂O] crystallizes in the monoclinic system as prismatic or bladed crystals with distinct rhombic form, and as arrowhead-shaped twins with beveled edges.  Pure selenite is colorless or white, but impurities create a range of pale grays, yellows, reds, and browns.  Selenite is transparent to translucent with a hardness of 1.5-2.0, perfect cleavage in one direction, vitreous to pearly luster, and a specific gravity of 2.3-2.4.  It occurs mainly in chemical-sedimentary, marine-evaporite formations of sandstone, limestone, or rock salt.

METAPHYSICAL PROPERTIES, LORE, USES: Selenite, along with other forms of gypsum, is used in plaster, soil conditioners, paint fillers, cement retardants, and drywall products.  According to modern metaphysical practitioners, selenite conveys white light that calms troubled minds, stabilizes emotions, and clarifies thoughts.

COLLECTORS’ INFORMATION:  The most collectible selenite crystals have water-clear transparency, a range of pale colors, and well-developed, rhombic crystals.

GLAUBERITE

HISTORY, NAME, LOCALITIES: Glauberite, pronounced GLOW-ber-ite (the first syllable rhymes with “cow”), was recognized as a mineral species in 1808 and named for German alchemist and chemist Johann Rudolf Glauber.  Glauberite is collected in Spain, Australia, Chile, Austria, Germany, and the United States (Arizona, California, Utah, New Jersey)

MINERALOGY, PROPERTIES, OCCURRENCE: Glauberite [sodium calcium sulfate, Na₂Ca(SO₄)₂] crystallizes in the monoclinic system as tabular or prismatic, steeply inclined, wedge-shaped, dipyramidal crystals.  Because many other evaporite minerals replace glauberite, it is one of the most widely pseudomorphed of all minerals.  Glauberite has a Mohs hardness of 2.5-3.0, perfect cleavage in one direction, a vitreous luster that is often covered with an efflorescent coating, and a specific gravity of 2.7-2.8.  It is transparent to translucent and colorless; crystals with efflorescent coatings are white.  Glauberite is sedimentary in origin and forms primarily as an evaporite mineral in marine and lacustrine deposits.  Small amounts of glauberite also occur in basaltic vugs and low-temperature hydrothermal veins.

METAPHYSICAL PROPERTIES, LORE, USES: Glauberite and other sodium-sulfate-containing minerals are mined as a source of sodium sulfate for use in the manufacture of paper, glass, and detergents.  Glauberite has no use in jewelry because of its softness, solubility in water, and tendency to effloresce.  Glauberite has no metaphysical significance.

COLLECTORS’ INFORMATION: Glauberite is popular among collectors for its distinctive crystal shapes and pseudomorphic forms.