Sun Stone Oligoclase (3) Raw Minerals Stones Rocks Collecting

Description

Origin : China

Sun-Stone or Oligoclase 41-55 gr - cm 3.5-5 Raw Minerals Stones Rocks for Collection.
Red variety of Oligoclase.

Oligoclase or Sun Stone is a rock-forming mineral belonging to the plagioclase feldspars.
Oligoclase is a high sodium feldspar that crystallizes in the triclinic system. The Mohs hardness is between 6 and 6.5, and the specific gravity is between 2.64 and 2.66. In color it is usually white, with shades of grey, green or red.
Oligoclase is a common mineral in the richest silica-rich varieties of igneous rock and in many metamorphic rocks.
A variety of it most frequently used as a gemstone is aventurine-feldspar or Sunstone which is found as reddish masses in southern Norway; this has a bright red to golden metallic shimmer, due to the presence of numerous small oriented hematite flakes within the feldspar structure.
Oligoclase occurs, often accompanying orthoclase, as a constituent of plutonic igneous rocks such as granite, syenite and diorite. It is found in porphyry and diabase dikes and sills as well as andesite and trachyte volcanic rocks. The best developed and largest crystals are those found with orthoclase, quartz, epidote and calcite in granite veins in Norway. Oligoclase is also found in metamorphic rocks formed under transitional conditions from greenschist to amphibolite facies. Some varieties are called moonstone and exhibit Schiller's iridescence due to the presence of exsolution lamellae during cooling.