Andalusite
Natural Faceted Gems
Andalusite is an aluminium silicate mineral and one of three minerals with the formula Al₂SiO₅. Transparent gem material can show strong pleochroism, displaying different green, brown, yellow or reddish colors when viewed along different crystal directions.
Identity
- Material or variety
- Andalusite
- Scientific or material identity
- Andalusite
- Classification
- Natural mineral or mineral variety
- Composition or formula
- Al₂SiO₅
- Crystal system or structure
- Orthorhombic
- Geological or manufacturing origin
- Forms or recrystallizes under metamorphic heat and pressure.
- Mohs hardness
- 7.5
Origins
Australia · Brazil · France · Madagascar · Spain · Sri Lanka · USA
Appearance & optical properties
transparent brown-green andalusite with pleochroic faces.
History & discovery
Jean-Claude Delamétherie named andalusite in 1798 for Andalusia, Spain, where he believed the studied specimens originated. The locality was mistaken: the material actually came from El Cardoso de la Sierra in Guadalajara. The name remained, while the true locality was corrected in later mineralogical work.
Uses & care
- Common uses
- Transparent crystals are faceted to combine their contrasting directional colors. Opaque chiastolite is cut across its crystal to display a dark cross, while most andalusite is used in heat-resistant furnace and kiln materials.
- Handling and cleaning
- Clean gem andalusite with warm water, mild soap and a soft brush. Although reasonably hard, it is brittle; protect facet edges from hard blows and avoid steam, ultrasonic cleaning and sudden temperature changes when inclusions or fractures are present.
Jewellery
5 pieces of Andalusite jewellery. Learners earn each one in DigMyGem by learning words; until then it shows as a silhouette.
Chameleon Stone Ring
Ring
An oval andalusite that shows green, gold and reddish-brown all at once, the pleochroism that gave the stone its reputation.
Andalusite Pendant
Pendant
An emerald-cut andalusite in rose gold, earthy amber-green with a warm flash at its centre.
Crossroads Earrings
Earrings
A pair of round andalusite cabochons, mottled olive and russet, one for each road the stone seems to hold.
Autumn Leaf Brooch
Brooch
An imagined leaf brooch set with andalusite, which shows green, gold and red at once like a turning leaf.
Andalusian Autumn Necklace
Necklace
An imagined gold necklace of andalusite, a stone that shows green, gold and red at once, named after Andalusia in Spain.