Andesine: The plagioclase feldspar mineral Andesine info & pictures

About

Andesine was named after its original occurrence in the Andes Mountains of South America. Andesine belongs to the Plagioclase Feldspar group, an isomorphous solid solution series. Albite is one member, containing sodium and no calcium. The other end member, Anorthite, contains calcium and no sodium. Andesine is an intermediary member of this series. Andesine is considered by some authorities as a variety of Albite rather than a separate mineral. The acclaimed Dana's System of Mineralogy lists Andesine as an individual mineral, whereas the IMA does not recognize it as individual mineral species, but rather a calcium-rich variety of Albite. Andesine is the primary feldspar constituent of the igneous rock Andesite.

Crystal Forms & Aggregates

Crystals, which are uncommon, are tabular and frequently twinned. Most often massive, grainy, as chunky masses, and as compact crystal groupings.

Striking Features

Crystal habits, cleavage, and hardness

Environment

In basalt rock and in andesites, also in metamorphic rocks.

Uses

There is a new gemstone called Andesine which has recently penetrated the market. Much of the material is Chinese in origin and has been synthetically diffused to enhance color, and is actually produced from Labradorite.

Noteworthy Localities

Andesine is prevalent in volcanic regions throughout the world. Its original locality in the Andes Mountains is the Marmato District, Manizales, Bolivia. Large crystals are found in the San Gabriel Mountains (Los Angeles County), California. Other localities are the Crestmore Quarry, Riverside County, California; Goodall Farm, Sanford, York County, Maine; Mont Saint Hilaire, Quebec, Canada; and Portland, Victoria, Australia.

Common Mineral Associations

Quartz, Muscovite, Biotite, Potassium Feldspar Group, Hornblende

Distinguishing Similar Minerals

Potassium Feldspar group - Don't exhibit striations on twinned crystal surfaces, whereas the Plagioclase feldspars do.
Other Plagioclase Feldspars - Usually cannot be determined by practical means.
Spodumene - Has a splintery cleavage.
Calcite - Much lower hardness.

Andesine

Abouti

Crystal Forms & Aggregatesi

Striking Featuresi

Environmenti

Usesi

Noteworthy Localitiesi

Common Mineral Associationsi

Distinguishing Similar Mineralsi

Photos