Legrandite Value, Price, and Jewelry Information

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0.68-ct legrandite, rectangular step cut, 5.4 x 4.3 mm, Mexico. © The Gem Trader. Used with permission.

Too soft for jewelry use, legrandite is a popular collector’s mineral because of its intense yellow color and aesthetic crystal groupings. Transparent, faceted gems are extremely rare.

Legrandite Information

Data Value
Name Legrandite
Crystallography Monoclinic. Crystals prismatic, also in sprays and fans.
Refractive Index 1.675-1.740
Colors Yellow, colorless.
Luster Vitreous
Hardness 4.5
Fracture Uneven
Specific Gravity 3.98-4.04
Birefringence 0.060
Cleavage Poor
Dispersion Distinct
Luminescence None
Luminescence Present No
Transparency Translucent to transparent
Absorption Spectrum Not diagnostic
Formula Zn2(OH)AsO4 · H2O.
Pleochroism Colorless to yellow
Optics a = 1.675-1.702; β = 1.690-1.709; γ = 1.735-1.740. Biaxial (+), 2V = 50°.
Optic Sign Biaxial +
Etymology Named after Louis C. A. Legrand, a Belgian mine manager who collected the first specimens.
Occurrence In vugs in limonite. Uncommon secondary mineral in the oxidized zone of arsenic bearing zinc deposits; rare in granite pegmatite.
legrandites and limonite

Legrandite crystals and limonite, Ojuela Mine, Mapimí, Mun. de Mapimí, Durango, Mexico. Photo by Géry Parent. Licensed under CC By-ND 2.0.

Does Legrandite Make a Good Jewelry Stone?

First described in 1932, legrandite has become one of the loveliest of all rare collector gemstones. Its yellow color is quite distinctive and appealing (but tends to appear splotchy). However, you’re more likely to find legrandites in a mineral collection than a jewelry collection.

With a relatively low hardness of 4.5, this gemstone has greater susceptibility to scratches than more popular jewelry stones. Protective settings would be advisable, but legrandites have another significant drawback as jewelry stones.

Legrandite: Mexico (0.55). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Is Legrandite Hazardous?

Legrandite contains arsenic. In inorganic mineral form, arsenic is especially dangerous, and ingestion is its most toxic exposure pathway. Due to legrandite’s low hardness, normal jewelry wear could easily scratch the stone. This could create tiny, loose particles that could be ingested accidentally. For this reason, jewelry use isn’t recommended.

Gem cutters should take special precautions while working with legrandites. Consult our lapidary safety tips for more information.

Displaying legrandites should pose no risks. However, make sure the specimens are secured beyond the reach of small children and pets.

legrandites

Legrandite crystals on display at the Houston Museum of Natural Science. Photo by Ed Uthman. Licensed under CC By 2.0.

Are There Synthetic Legrandites?

There are no known synthetic legrandites or treatments for these gems.

Where are Legrandites Found?

To date, only Mexico has produced cuttable material. Legrandite was first discovered in the Flor de Peña Mine, Nuevo León. However, the best-known gem locality is the Ojuela Mine, Mapimí. It produces magnificent crystal clusters, single crystals up to 6 cm long and 7.5 mm thick.

legrandite - type locality

Legrandites from the type locality, Flor de Peña Mine, Lampazos, Nuevo León, Mexico, 4.0 x 3.0 x 2.0 cm. © Rob Lavinsky, www.iRocks.com. Used with permission.

Other notable crystal sources include the following:

  • Minas Gerais, Brazil; Japan; Tsumeb, Namibia; Sterling Hill, New Jersey, USA.

Stone Sizes

The largest faceted legrandites range from 2 to 4 carats in size, although a 10-ct stone has been reported. Still, larger cut stones are great rarities, and even 1-ct gems are hard to find.

Legrandite: Mexico (1.3). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Transparent crystals are usually small in size. The larger the crystal, the more opaque (translucent) it becomes. Many mineral specimens exist. However, transparent crystals occur very rarely, even at the source locality.

Legrandite - faceted and rough - Mexico

Legrandite: Mexico (~ 2, rough 1½ inches long). Photo © Joel E. Arem, PhD, FGA. Used with permission.

How to Care for Legrandites

Clean legrandites only with warm water, mild detergent, and a soft brush. For more recommendations, consult our gemstone jewelry care guide.

legrandite- Ojuela Mine

Legrandites, Ojuela Mine, Mapimí, Durango, Mexico, 6.4 x 4.6 x 3.2 cm. © Rob Lavinsky, www.iRocks.com. Used with permission.

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