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| Chemistry:
CaAl2Si2O7(OH)2·(H2O)
[Hydrated
Calcium Aluminum Silicate] | Discovered
in 1895;
IMA
status: Valid (pre-IMA; Grandfathered). Lawsonite
is named for
Professor Andrew Cowper Lawson (1861-1952), Scottish-American
geologist, University of California, Berkeley, California,
USA. |
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Classification
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Mineral
Classification: |
Silicates |
Strunz 8th
Ed. ID:
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8/C.10-10
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Nickel-Strunz 10th
Ed. ID:
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9.BE.05 |
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9 : SILICATES (Germanates) B : Sorosilicates E :
Si2O7 groups, with additional anions; cations in
octahedral [6] and greater coordination
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Related
to: |
Lawsonite - Ilvaite Series.
Dimorphous with Parthéite.
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Crystal
Data
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Crystallography:
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Orthorhombic
- Dipyramidal
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Crystal
Habit:
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Crystals
commonly prismatic, tabular, to 5 cm; also granular,
massive.
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Twinning:
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Common
on [101], may be lamellar.
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Physical
Properties
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Cleavage: |
[100]
Perfect, [010] Perfect, [101] Imperfect
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Fracture: |
Irregular/Uneven
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Tenacity:
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Brittle
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Hardness
(Mohs): |
7.5
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Density:
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3.05
- 3.12 (g/cm3)
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Luminescence:
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None |
Radioactivity:
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Not
Radioactive
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Optical
Properties
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Color: |
Colorless,
White, Grayish Blue, pale Blue, Pinkish
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Transparency: |
Transparent,
Translucent |
Luster: |
Vitreous,
Greasy |
Refractive
Index: |
1.663
- 1.686 Biaxial ( + )
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Birefringence: |
0.0190
- 0.0210
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Dispersion: |
Strong
to Very Strong |
Pleochroism: |
Weak;
X
= blue, pale brownish yellow; Y
= deep bluish green, yellowish green; Z
= colorless, yellowish |
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Occurances
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Geological
Setting: |
Formed
at high pressures and low temperatures, especially in
low-grade regionally metamorphosed glaucophane schists;
formed from plagioclase during saussuritization of gabbros
and diabases; rarely in eclogites. |
Common
Associations: |
Calcite,
Crossite, Epidote, Garnet, Glaucophane, Jadeite, Muscovite,
Pumpellyite, Quartz |
Type
Locality: |
Reed Station, Tiburon Peninsula, Marin County, California,
USA |
Year
Discovered: |
1895
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View
mineral photos: |
Lawsonite
Mineral Photos and Locations |
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More
Information
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Mindat.org Webmineral.com |
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Lawsonite
is a very rare silicate mineral that is only found in
a few locations worldwide. Gems are extremely rare and
can be attractive with colorless, pale blue or pinkish
colors and strong dispersion.
The
main location for gem quality crystals is the type locality
at Reed Station, Tiburon Peninsula, Marin County, California,
USA. Other locations include Panoche Pass, San Benito County; in the Pacheco
Pass area, Santa Clara County, California, USA; Darrington,
Snohomish County, Washington, USA; the French and Italian
Alps; and near Tavsanh, Turkey.
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Lawsonite
gems for sale:
We
have not photographed our Lawsonite
gems. Please
check back soon.
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