Lawsonite

Lawsonite is a hydrous calcium aluminium sorosilicate mineral with formula CaAl2Si2O7(OH)2·H2O. Lawsonite crystallizes in the orthorhombic system in prismatic, often tabular crystals. Crystal twinning is common. It forms transparent to translucent colorless, white, and bluish to pinkish grey glassy to greasy crystals. Refractive indices are nα=1.665, nβ=1.672 - 1.676, and nγ=1.684 - 1.686. It is typically almost colorless in thin section, but some lawsonite is pleochroic from colorless to pale yellow to pale blue, depending on orientation. The mineral has a Mohs hardness of 8 and a specific gravity of 3.09. It has perfect cleavage in two directions and a brittle fracture.

Lawsonite is a metamorphic mineral typical of the blueschist facies. It also occurs as a secondary mineral in altered gabbro and diorite. Associate minerals include epidote, titanite, glaucophane, garnet and quartz. It is an uncommon constituent of eclogite.

It was first described in 1895 for occurrences in the Tiburon peninsula, Marin County, California. It was named for geologist Andrew Lawson (1861-1952) of the University of California by two of Lawson's graduate students, Charles Palache and Frederick Leslie Ransome.

Read more about LawsoniteComposition, Geologic Occurrence, Crystal Structure, Physical Properties, Significance of Lawsonite

Other articles related to "lawsonite":

Eclogite Facies
... Eclogites containing lawsonite (a hydrous calcium-aluminium silicate) are rarely exposed at Earth's surface, although they are predicted from experiments and thermal models to form during normal subduction of ... The rarity of lawsonite eclogites therefore does not reflect unusual formation conditions but unusual exhumation processes ... Lawsonite eclogite is known from the U.S ...
Significance of Lawsonite
... Lawsonite is a significant metamorphic mineral as it can be used as an index mineral for high pressure conditions ... Lawsonite is known to form in high pressure, low temperature conditions, most commonly found in subduction zones where cold oceanic crust subducts down oceanic trenches into the mantle (Comodi et al ...