Lawsonite: The mineral lawsonite information and picture

About

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.

Crystal Forms & 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.

Striking Features

Localities, perfect cleavage, color, and hardness.

Environment

In metamorphosed blue schists, as well as altered gabbros and basalt.

Varieties

✓ common · ✗ uncommon

Chromian Lawsonite— 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.