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Yugawaralite
Current inventory:  0 gems
 

Chemistry:  CaAl₂Si₆O₁₆ • 4H₂O

Discovered in 1952 ;   IMA status: Valid (pre-IMA; Grandfathered).
Yugawaralite is named for the locality where it was first discovered: Yugawara Hot Springs, Kanagawa Prefecture, Honshu, Japan.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/J.25-90

8 : SILICATES
J: Tektosilicates with zeolitic H₂O; zeolite family
25: Chains of single connected 4-membered rings

90: Zeolite Group (Laumontite Subgroup)

Crystal Data

Crystallography:

Monoclinic - Domatic

Crystal Habit:

Crystals are flat tabular, to 8 cm; in groups of nearly parallel crystals

Twinning:

None

Physical Properties

Cleavage:

[100] Distinct, [101] Imperfect, [010] Indistinct (parting)

Fracture:

Conchoidal

Tenacity:

Very Brittle

Hardness (Mohs):

4.5 - 5.0

Density:

2.20 - 2.25 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Piezoelectric and pyroelectric

Optical Properties

Color:

Colorless, White, Pinkish

Transparency:

Transparent to Translucent

Luster:

Vitreous, Pearly

Refractive Index:

1.492 - 1.504  Biaxial ( + )

Birefringence:

0.0090

Dispersion:

Weak to Distinct; r < v

Pleochroism:

None

Occurances

Geological Setting:

As crystals lining cavities, and veinlets, typically deposited in active geothermal areas.

Type Locality:

Yugawara Hot Spring, Kanagawa Prefecture, Kanto Region, Honshu Island, Japan

Year Discovered:

1952

View mineral photos:

Yugawaralite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Yugawaralite is an extremely rare member of the Zeolite Group of minerals that includes over 40 minerals and these gem-type minerals: Analcime, Barrerite, Chabazite, Epistilbite, Gmelinite-Na, Goosecreekite, Mordenite, Natrolite, Pollucite, Scolecite, Stellerite, Stilbite, Thomsonite and Yugawaralite.

Yugawaralite crystals are only found in a few locations worldwide and few of these are facetable. Sources include Japan (the Type Locality); Bombay, India; Alaska; Iceland; Sardinia; British Columbia. The best source for facet grade crystals is probably the Khandivali Quarry, near Bombay, India where well-formed, colorless, transparent crystals up to 3 cm have been found.
 

  
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