Mineralpedia Details for Lawsonite

Named after Professor Andrew Cowper Lawson, a Scottish-American geologist at the University of California in the United States. Lawsonite is an uncommon mineral that occurs at high pressures and low temperatures in regionally metamorphosed, low-grade, glaucophane-bearing schists. It can also form from plagioclase during its alteration to saussurite in gabbro and diabases and can be found rarely in eclogite. Localities include in the USA, localities in the French-Italian Alps, Turkey, Japan, New Caledonia, and on Celebes Island.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/lawsonite.pdf

Formula

CaAl₂Si₂O₇(OH)₂·H₂O 

Crystal System

Orthorhombic 

Crystal Habit

Prismatic, Tabular 

Cleavage

Perfect, Perfect, Poor 

Luster

Vitreous - Greasy 

Color

colorless, white, gray, blue, pinkish 

Streak

white 

Class

Orthorhombic - Dipyramidal 

Fracture

Brittle - Uneven 

Hardness

7.5 

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Mindat

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Light purplish well formed Lawsonite crystals to 5mm richly covering the top side of green Glaucophanitic-Schist matrix.