Gypsum Value, Price, and Jewelry Information
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.
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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.
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Does Gypsum Make a Good Jewelry Stone?
Gypsums are best reserved for display in a gem or mineral collection. Jewelry use isn't recommended.
Gypsum's physical properties make it a very unlikely choice for jewelry use. To begin with, faceting this mineral is extremely challenging. 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).
Gypsum's optical properties don't improve its jewelry prospects. Gypsum stones 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 and a wonderful showcase of the art of faceting. You're more likely to find gypsum cabbed than faceted, but these pieces would still be best reserved for display only.
Gypsum Varieties
On the other hand, gypsum's physical properties make some of its varieties very desirable for carvings and other decorative objects. In addition, gypsums can also occur in attractive crystals that may appeal to collectors. These crystals can have very unusual natural shapes and may also show astonishing "water-like" transparency.
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.
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").
Selenite
Colorless, transparent gypsum crystals are called selenite. Any rare, faceted gypsums would most likely be selenites.
"Ram's Horn"
Gypsum crystals may form in curved shapes that resemble the horns of a ram.
"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.
Is Gypsum Luminescent?
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: blueish, 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 blueish 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.
How to Distinguish Calcite from Gypsum
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).
Is There Synthetic Gypsum?
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.
Gypsum can take dyes and coatings very easily.
Where is Gypsum Found?
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 over 13 tons. In 2015, the cave was re-flooded and closed to further exploration.
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.
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).
How to Clean Gypsums
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.
Joel E. Arem, Ph.D., FGA
Dr. Joel E. Arem has more than 60 years of experience in the world of gems and minerals. After obtaining his Ph.D. in Mineralogy from Harvard University, he has published numerous books that are still among the most widely used references and guidebooks on crystals, gems and minerals in the world.
Co-founder and President of numerous organizations, Dr. Arem has enjoyed a lifelong career in mineralogy and gemology. He has been a Smithsonian scientist and Curator, a consultant to many well-known companies and institutions, and a prolific author and speaker. Although his main activities have been as a gem cutter and dealer, his focus has always been education. joelarem.com
International Gem Society
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