Gypsum Value, Price, and Jewelry Information


step-cut gypsum - Peru
Step-cut colorless gypsum, 43.44 cts, 33.4 x 20 mm, Peru. © The Gem Trader. Used with permission.

Gypsum is one of the most abundant minerals, but gem-quality crystals are very rare. This material is extremely difficult to facet but very easy to carve into sculptures and decorative objects.

Gypsum Value

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Gypsum Information

DataValue
NameGypsum
VarietiesAlabaster, Satin Spar, Selenite
Alternate Common NamesVarieties: alabaster, satin spar, selenite.
Crystallography Monoclinic. Crystals often perfect and large; tabular; rosettes; lenticular; helictites are grotesque shapes found in caves; often twinned; massive; granular.
Refractive Index 1.520-1.530
Colors Colorless, white, gray, black; impurities make it yellowish, reddish, brownish, greenish, pink, bluish, orangish. Sometimes banded and patterned like marble.
Luster Subvitreous; pearly on cleavages.
Polish Luster Waxy to subvitreous.
Fracture Luster Dull to pearly.
Fracture Granular, uneven
Hardness 1.5 to 2, varies with direction.
Specific Gravity 2.32 (range 2.30-2.33)
Birefringence 0.010
Cleavage Perfect and easy, 1 direction; distinct 2 other directions
Dispersion 0.033
Heat SensitivityYes.
Luminescence May show fluorescence and sometimes phosphorescence. Can show a wide range of colors in SW and LW, the most commonly encountered are bluish, orange-yellow, yellow, greenish, and brownish. Selenite crystals often exhibit zoned "hourglass" fluorescence that may, or may not, be evident in ordinary light. Inert in X-rays.
Wearability Poor
Enhancements Dyeing, common. Bleaching, common. Coating. Occasional heating to improve color, prepare for dying.
Transparency Transparent to Opaque
Absorption Spectrum Not diagnostic.
Phenomena Chatoyant.
FormulaCaSO4 2H2O.
Pleochroism None.
Optics a = 1.520; β = 1.523;  γ = 1.530. Biaxial (+), 2V= 58°.
EtymologyGypsum from the Greek gypsos, a name applied to what we now call plaster. Satin spar in allusion to the satiny luster of the fibrous material. Selenite from the Greek selene for “moon,” due to the pearly luster on cleavage surfaces. Alabaster from the Greek alabastros, a stone used to make ointment vases.
OccurrenceIn sedimentary rocks and deposits; saline lakes; oxidized parts of ore deposits; volcanic deposits.
gypsum crystals - Mexico
Gypsum: Mexico (specimen ~ 2 inches high). © Joel E. Arem, PhD, FGA. Used with permission.

Comments

Gypsum’s physical properties make it extremely challenging to facet. It has perfect and easy cleavage in three directions and, depending on its orientation, a tenacity that can make it either bendable or breakable. It’s both water soluble and very heat sensitive. Gypsum also famously represents the hardness of 2 on the Mohs scale, which means it’s very easy to scratch. (In some directions, gypsum may actually have an even lower hardness of 1.5).

For these same reasons, gypsums would make unlikely choices for jewelry use. In addition, they usually show no attractive colors, though impurities may add pale shades. This material has a surprisingly high dispersion of 0.033 but just can’t receive a cut to show it off. Of course, a faceted piece would make a rare addition to a mineral or gem collection. Crystals can occur in very unusual natural shapes and may also show astonishing “water-like” transparency.

selenite crystal, colorless gypsum - Mexico
Selenite (colorless gypsum crystal) with incredible transparency. 20.0 x 10.0 x 10.0 cm. Naica, Chihuahua, Mexico. © Rob Lavinsky, www.iRocks.com. Used with permission.

Alabaster

Artisans have used this massive, granular variety of gypsum for thousands of years to make objects such as bowls, vases, and sculptures. Alabaster is very easy to carve and is used today for ashtrays, clock housings, paperweights, and so forth. Carved alabaster objects still have a very low softness. However, scratches on these can be polished out rather more easily than on small stones. (Please note: the term “alabaster” sometimes refers to a form of opalescent glass, likely due to its appearance. Glass and gypsum, however, have very distinct properties).

Mesopotamian alabaster relief - gypsum
Relief sculpture of a lamassu, a human-headed winged bull, made from gypsum alabaster. Neo-Assyrian, Mesopotamia, ca. 883–859 BCE, 313.7 x 67.3 x 309.9 cm and 7,257.4 kg. Gift of John D. Rockefeller Jr., 1932. Metropolitan Museum of Art, New York. Public Domain.

Satin Spar

This massive, fibrous variety of gypsum can be carved or cabbed. Brown satin spar can make lovely decorative items. Some satin spar cabochons may show very pronounced chatoyancy or a “cat’s eye” effect. The noted mineralogist and folklorist George F. Kunz wrote that egg-shaped satin spar cabs from Egypt were sometimes called “Pharaoh’s Eggs” and were purported to be lucky, just like satin spar cabs from Niagara Falls — supposedly recovered from gypsum deposits beneath the waterfalls at great peril. (These tourist stones were sometimes called “Niagara spar”).

satin spar cabochon - gypsum
Polished satin spar (gypsum). Photo by Paul Williams. Licensed under CC By 2.0.

Selenite

Colorless, transparent gypsum crystals are called selenite. Those rare, faceted gypsums would most likely be considered selenites.

selenite crystals on alabaster - gypsum specimen - Spain
This striking specimen has two transparent selenite crystals emerging from a matrix of alabaster. (You can see the matrix and the wall clearly through the selenites). Large crystal, 2.9 cm, specimen 4.6 x 4.4 x 3.0 cm, Alabaster quarries, Cerro Patillas, Fuentes de Ebro, Zaragoza, Aragon, Spain. © Rob Lavinsky, www.iRocks.com. Used with permission.

“Ram’s Horn”

Gypsum crystals may form in curved shapes that resemble the horns of a ram.

"Ram's horn" gypsum - China
“Ram’s horn” selenite crystal, 9.7 x 8.2 x 4.6 cm, Guangdong Province, China. © Rob Lavinsky, www.iRocks.com. Used with permission.

“Desert Rose”

In desert regions, minerals such as barite and gypsum can occur as tabular crystals with rose-like shapes. (The crystals form the petals of the rose, so to speak). These stones contain trapped sand particles.

desert rose - gypsum
Gypsum “desert rose.” Photo by Stephanie Clifford. Licensed under CC By 2.0.

Identifying Characteristics

Some gypsums, but not all, may luminesce, showing both fluorescence and phosphorescence. They may show a wide range of colors in shortwave (SW) and longwave (LW) ultraviolet light (UV). The most commonly encountered include the following: bluish, orange-yellow, yellow, greenish, and brownish. Gypsums are inert in X-rays.

A twinned selenite crystal growing from a ball of selenite crystals. These selenites fluoresce bluish green in UV light and also phosphoresce. 3.2 x 2.0 x 1.8 cm, Block and Brady One Pit, Red River Floodway, near, Winnipeg, Manitoba, Canada. © Rob Lavinsky, www.iRocks.com. Used with permission.

Selenite crystals often exhibit zoned “hourglass” fluorescence that may, or may not, be evident in ordinary light.

Both calcite and gypsum are abundant but rarely faceted minerals. As transparent crystals and faceted gems, they may look very similar, especially when colorless. (Calcites have a wider and richer range of colors). Although calcite has a higher hardness (3) than gypsum, a scratch test may not be the best way to test a potentially rare faceted specimen. A specific gravity (SG) test can easily distinguish these gems. Calcite has a higher SG range (2.71-2.94) than gypsum (2.30-2.33).

Synthetics

Gypsum has a myriad practical uses and a long history of industrial applications. Despite its abundance, gypsum is also widely synthesized — as an industrial by-product — for many purposes. However, there’s no known jewelry use for this synthetic material.

Of course, gypsum’s physical properties make it an unlikely choice for synthetic jewelry material. However, gypsums may be encountered as simulants or imitations of other more valuable or well-known gemstones. For example, gypsum has been used in the manufacture of assembled cabochons designed to imitate rainbow moonstones. 

Enhancements

Gypsum can take dyes and coatings very easily.

Sources

The most common sulfate mineral, gypsum has many sources all over the world. It occurs especially in evaporite environments.

One of the most celebrated occurrences, the “Cave of the Crystals” in Naica, Chihuahua, Mexico contains gigantic selenite crystals. The largest found so far measures 39’ x 13’ and weighs 55 tons.

Cave of the Crystals, giant gypsum crystals - Naica, Mexico
Giant gypsum (selenite) crystals in the “Cave of the Crystals” in Naica, Chihuahua, Mexico. Note the person for scale. Photo by Alexander Van Driessche. Licensed under CC By 3.0.

Other gem-quality sources include the following:

  • United States: Arizona; California (many locations); Colorado; Kansas; Michigan; New Mexico; New York; South Dakota; Utah; other states.
  • Australia; Canada; Braden, Chile (crystals reported up to 10’ long); China; Czech Republic; Egypt; Germany; Peru; Russia; Spain.

Notable sources of alabaster include Tuscany, Italy and England, United Kingdom.

gypsum crystals - Canada
A specimen of golden, transparent gypsums, with twin crystals emerging from a ball of smaller gypsum crystals. 5.1 x 4.4 x 3.8 cm. Red River Floodway, Winnipeg, Manitoba, Canada. © Rob Lavinsky, www.iRocks.com. Used with permission.

Stone Sizes

Lapidaries could cut cabochons and carvings of almost size desired from massive gypsum. Fibrous material could yield large carvings up to several pounds. Faceted selenites could reach hundreds of carats, since large transparent crystals do exist. (Only the fragile nature of the material limits the finished size).

Care

Gypsums are best reserved for display in a gem or mineral collection. Jewelry use isn’t recommended.

Never use mechanical systems, which use heat or vibrations, to clean any gypsum pieces. Since the material can be quite porous, clean by hand and only with warm water with no detergents. Pat dry carefully; don’t rub or scrub the piece.

For more care recommendations, consult our gemstone jewelry cleaning guide.

gypsum sculpture - Iran
Seated baboon sculpture, gypsum inlaid with steatite, 4″, Iran, Elamite, second half of 3rd millennium BCE. From the Art of the Ancient Near East collection, the Los Angeles County Museum of Art. Public Domain.