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.

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.

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.

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.