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Petalite
Current inventory:  0 gems
 

Chemistry:  LiAlSi₄O₁₀  []

Discovered in 1800;   IMA status: Valid (pre-IMA; Grandfathered).
The name Petalite is from the Greek petalos meaning leaf in regard to its perfect basal cleavage. The name for the crystals that Petalite is cut from is Castorite, named after Castor. Castor and Pollux were heavenly twins and brothers of Helen of Troy from Greek mythology.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/J.03-10

Nickel-Strunz 10th Ed. ID:

9.EF.05

9 : SILICATES (Germanates)
E : Phyllosilicates
F : Single nets with 6-membered rings, connected by M[4], M[8], etc.

Related to:

Petalite - Virgilite Series

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals tabular on [010], or elongated, to 2 m; some faces may be striated. Commonly foliated cleavable, massive.

Twinning:

Common on [001], lamellar

Physical Properties

Cleavage:

[001] Perfect, [201] Imperfect

Fracture:

Imperfectly Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

6.0 - 6.5

Density:

2.412 - 2.422 (g/cm³)

Luminescence:

Thermoluminescent

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, Gray, Yellow, Pink

Transparency:

Translucent to Transparent

Luster:

Vitreous, Pearly on cleavages

Refractive Index:

1.504 - 1.523  Biaxial ( + )

Birefringence:

0.0120 - 0.0140

Dispersion:

Weak; r > v

Pleochroism:

None

Occurances

Geological Setting:

In granite pegmatites, locally constituting an ore of lithium.

Common Associations:

Albite, Spodumene, Lepidolite, Microcline, Pollucite, Quartz, Topaz, Tourmaline

Common Impurities:

Mg,Fe,Na,Ca,K,H₂O

Type Locality:

Utö Island, Haninge, Södermanland, Sweden

Year Discovered:

1800

View mineral photos:

Petalite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Petalites are beautiful colorless gems which are usually free of inclusions. They are bright white and somewhat rare. Petalite gems could be used in jewelry, but with care since they are a bit brittle. Most gem quality Petalite is currently coming from Brazil.

The name Petalite is from the Greek petalos meaning leaf in regard to its perfect basal cleavage. The name for the crystals that Petalite is cut from is Castorite, named after Castor. Castor and Pollux were heavenly twins and brothers of Helen of Troy from Greek mythology. Pollux is the basis for the naming of Pollucite.

The main sources of gem quality crystals are Paprok, Nuristan Province, Afghanistan; Bahia, Northeast Region, Brazil; Minas Gerais, Southeast Region, Brazil; and Mogok, Sagaing District, Mandalay Division, Burma (Myanmar).
 
 

  
Petalites gems for sale:

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