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Lawsonite Crystals in Matrix

The Mineral lawsonite




Lawsonite is a rare mineral, and is a hydrated variant of the feldspar Anorthite. It is named after Andrew Cowper Lawson (1861-1952), a professor of geology at the University of California at Berkeley. The Bay Area of California is the type locality and primary region of this mineral, and this is where Lawson taught. Lawson's main claim to fame is his identification and naming of the San Andreas Fault.
Chemical Formula CaAl2Si2O7(OH)· H2O
Composition Hydrous basic calcium aluminum silicate
Color Light blue, light pink, light purple, gray, tan, or white. May also be multicolored with color zoning of light blue, light pink, or light purple. Rarely bright green or bluish-green.
Streak White
Hardness 7.5
Crystal System Orthorhombic
Crystal Forms
and Aggregates
Crystals are usually prismatic or tabular, and they are often crude and of grainy appearance. Also in groupings of stubby or tabular crystals. May also be granular and massive. Crystals are sometimes twinned.
Transparency Transparent to translucent
Specific Gravity 3.1
Luster Vitreous
Cleavage 1,2;3,3
Fracture Uneven
Tenacity Brittle
In Group Silicates; Sorosilicates
Striking Features Localities, perfect cleavage, color, and hardness.
Environment In metamorphosed blue schists, as well as altered gabbros and basalt.
Rock Type Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 3


Lawsonite AUCTIONS

VARIETIES
 -  A bright green, chromium-rich variety of Lawsonite, described from Syros Island, Greece.


USES
Lawsonite is used in geological studies to determine the formation and metamorphism of certain rock formations.

NOTEWORTHY LOCALITIES
Lawsonite is a not commonly represented in collections, though this mineral is probably more widespread than perceived. In the U.S., the only significant localities are in the Coast Ranges area of Central California. Large, pale blue crystals of Lawsonite were found at the type locality near the Reed Station in the Tiburon Peninsula, Marin Co., California. This locality has since been built over and is no longer in existence. Light tan and pink crystals have come from Valley Ford, Sonoma Co., California. A deep green, chromium-rich form of Lawsonite was reported as newly discovered material from Cape Marmari, Syros Island, Greece, in 2010.

COMMON MINERAL ASSOCIATIONS
Glaucophane, Chlorite, Almandine, Muscovite, Actinolite

DISTINGUISHING SIMILAR MINERALS
Celestine - Much software, primarily a sedimentary mineral.
Feldspars - Softer.



lawsonite PHOTOS
 
ADDITIONAL RESOURCES
 
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