2.6" Rare Andalucite Var Chiastolite Mineral Specimen Asturias Province Boal Spain

Location: Asturias Province, Boal, Spain

Weight: 5 Ounces 

Dimensions: 2.6 Inches Long, 3 Inches Wide, 1.3 Inches Thick

The item pictured is the one you will receive. 

Andalucite, an important mineral within geology and mineralogy, is named after Andalusia, the southern Spanish region where it was originally discovered and documented. This aluminum nesosilicate is distinguished by its unique crystal structure and develops under particular metamorphic conditions. Its occurrence in Spain, especially within Andalusia, has been vital in elucidating its geological background and its significance as an indicator mineral.

Andalucite is one of the three polymorphs of Al2SiO5, alongside kyanite and sillimanite. While these polymorphs share an identical chemical composition, they differ in crystal structure, each stable under distinct pressure and temperature conditions. Andalucite commonly occurs in medium-grade metamorphic rocks, typically linked to regional metamorphism. Its presence signifies a particular range of pressure and temperature during rock formation, rendering it an essential marker for geologists investigating metamorphic processes.

The crystal system of andalucite is orthorhombic, meaning its crystals have three axes of unequal length that are mutually perpendicular. Common crystal habits include prismatic forms, often with a square cross-section. The color of andalucite can vary, ranging from pink, red, and violet to brown, green, and even colorless. This variability in color is often due to the presence of trace elements within its crystal lattice. A notable variety of andalucite is chiastolite, which exhibits a distinctive cruciform pattern of dark carbonaceous inclusions within the lighter mineral. This pattern is a result of the growth mechanism of the crystal, where impurities are preferentially incorporated along specific crystallographic directions