The rarest plagioclase feldspar, anorthite is very rarely faceted.
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Anorthite is the most calcium-rich/sodium-poor plagioclase feldspar (90-100% Ca/10-0% Na). It forms a solid solution series with sodium-rich/calcium-poor albite (90-100% Na/10-0% Ca). The other plagioclase stones — oligoclase, andesine, labradorite, and bytownite — have intermediate compositions.
Although anorthites occur in many locations throughout the world, in many rock types and environments, it's the rarest plagioclase. Its crystals are seldom transparent. As a result, anorthites cut into gemstones are an extremely rare sight.
Some plagioclases, like labradorite, make popular gemstones. Nevertheless, with a hardness of 6 to 6.5 and perfect cleavage in two directions and imperfect in another, anorthites are still susceptible to damage from scratches and blows against hard surfaces. As ring stones, anorthites would need protective settings. Use for earrings, pendants, and brooches would be more advisable.
Of course, you're more likely to find anorthites in a mineral collection than a jewelry collection.
Scientists have synthesized anorthite crystals for mineralogical research. However, there's no known jewelry use for this material.
Notable sources include the following:
Rare, faceted gems are always small. However, a locality on Great Sitkin Island, Alaska has yielded cut gems as large as eight carats. This pale yellow anorthite may be the largest known.
Due to their cleavage, avoid cleaning anorthites with mechanical cleaning systems, like steam and ultrasound. Clean them only with a soft brush, mild detergent, and warm water. Consult our gemstone jewelry cleaning guide for more recommendations.
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Anorthite is the most calcium-rich/sodium-poor plagioclase feldspar (90-100% Ca/10-0% Na). It forms a solid solution series with sodium-rich/calcium-poor albite (90-100% Na/10-0% Ca). The other plagioclase stones — oligoclase, andesine, labradorite, and bytownite — have intermediate compositions.
Although anorthites occur in many locations throughout the world, in many rock types and environments, it's the rarest plagioclase. Its crystals are seldom transparent. As a result, anorthites cut into gemstones are an extremely rare sight.
Some plagioclases, like labradorite, make popular gemstones. Nevertheless, with a hardness of 6 to 6.5 and perfect cleavage in two directions and imperfect in another, anorthites are still susceptible to damage from scratches and blows against hard surfaces. As ring stones, anorthites would need protective settings. Use for earrings, pendants, and brooches would be more advisable.
Of course, you're more likely to find anorthites in a mineral collection than a jewelry collection.
Scientists have synthesized anorthite crystals for mineralogical research. However, there's no known jewelry use for this material.
Notable sources include the following:
Rare, faceted gems are always small. However, a locality on Great Sitkin Island, Alaska has yielded cut gems as large as eight carats. This pale yellow anorthite may be the largest known.
Due to their cleavage, avoid cleaning anorthites with mechanical cleaning systems, like steam and ultrasound. Clean them only with a soft brush, mild detergent, and warm water. Consult our gemstone jewelry cleaning guide for more recommendations.
The rarest plagioclase feldspar, anorthite is very rarely faceted.
