Yugawaralite Value, Price, and Jewelry Information

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Yugawaralite, 1.01 cts. Photo © Joel E. Arem, PhD, FGA. Used with permission.

Yugawaralite

Yugawaralite is a very rare colorless to pinkish zeolite mineral. Little facetable material exists, so a cut yugawaralite would be a prized addition to a gem collection.

Yugawaralite Information

Data	Value
Name	Yugawaralite
Is a Variety of	Zeolite
Crystallography	Monoclinic: crystals tabular and very flat.
Refractive Index	1.495-1.504
Colors	Colorless, white, pinkish.
Luster	Vitreous.
Hardness	4.5
Fracture	Conchoidal
Specific Gravity	2.23-2.25
Birefringence	0.009
Cleavage	Imperfect
Dispersion	Weak.
Luminescence	None reported.
Luminescence Present	No
Transparency	Transparent.
Absorption Spectrum	None.
Formula	CaAl₂Si₆O₁₆ · 4H₂O.
Pleochroism	None.
Optics	a = 1.495; β = 1.497; γ = 1.504. Biaxial (+).
Optic Sign	Biaxial +
Etymology	Named after its type locality, Yugawara Hot Spring, Japan.
Occurrence	In veins and crystals in volcanic rocks (Japan) and in huge crystals in breccia cavities (India).

Yugawaralite from Mumbai, India, from the collection of the A. E. Seaman Mineral Museum, Houston, Michigan. Photo by Chris857. Licensed under CC By-SA 3.0.

Comments

The Kandivali Quarry near Mumbai, India has produced superb, well-formed colorless and transparent crystals close to the literature values for yugawaralite. A few faceted gems have been cut from this exceptional and extremely rare material.

Identifying Characteristics

Yugawaralites have both pyroelectric and piezoelectric properties. This means they generate electricity when heated and placed under pressure, respectively.

Transparent, tabular yugawaralite crystals, the longest measure 0.7 mm. Malad Quarry (Kandivali Quarry), Malad, Ward 38, Mumbai (Bombay), Mumbai District (Bombay District), Maharashtra, India. Photo by Gianfranco Ciccolini. Public Domain.

Synthetics

Scientists have synthesized yugawaralites as well as other zeolites for chemical and mineralogical research. However, there is no known jewelry use for this synthetic material.

Enhancements

None known.

Sources

Japan, notably Honshu Island, produces gemmy material. Yugawara Hot Spring, Kanagawa Prefecture is the type locality for yugawaralite.

India, most notably the Kandivali Quarry, produces small amounts of facetable material.

Other notable crystal sources include the following:

United States: Alaska; Washington; Yellowstone National Park, Wyoming.
British Columbia, Canada; Iceland; Sardinia, Italy; Réunion Island.

Yugawaralite (picture width: 20 x 10 mm), Cirque de Cilaos, Piton des Neiges, Réunion Island. Photo by Michel Poullaouec. Public Domain.

Stone Sizes

The Kandivali Quarry can produce gem-quality crystals up to 3 cm long.

Care

You’re more likely to find yugawaralites, if at all, in gem collections than jewelry collections. If used in jewelry, these stones would require protective settings and occasional wear only. Their hardness of 4.5 means they can be scratched very easily, and their very brittle tenacity means they’re more likely than most gems to fracture from impact. Clean these gemstones only with a warm damp cloth, mild detergent, and soft brush. For more care recommendations, consult our gemstone jewelry cleaning guide.

Yugawaralite from Toi-cho, Shizuoka Province, Japan, on display at the Natural History Museum, Berlin. Photo by Alice Chodura. Licensed under CC By-SA 3.0.