56g Staurolite fairy cross crystal on mica matrix from Kola peninsula 54x48 mm.

Description

Locality: Pestsovye Keivy, Keivy Mountains, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia
Weight: 56 g / 1,96 oz
Dimensions: 54 x 48 x 17 mm / 2,1 x 1,9 x 0,7 inch
Staurolite is a silicate mineral with a generalized chemical composition of (Fe,Mg)2Al9Si4O23(OH). It is usually brown or black in color with a resinous to vitreous luster. It ranges from transparent to opaque in diaphaneity.
Staurolite is usually easy to identify when it occurs as visible grains in a metamorphic rock. Grains of staurolite are typically larger than the grains of other minerals in the rock, and they often exhibit an obvious crystal structure. They occur as six-sided crystals, often with penetration twins.
The name "staurolite" is from the Greek word "stauros," which means "cross." The mineral commonly occurs as twinned, six-sided crystals that sometimes intersect at 90 degrees to form a cross. (An intersection angle of 60 degrees is more common.) In some localities these twinned crystals are collected, made into jewelry, and sold under the name "fairy crosses."