2" Rare Andalucite Var Chiastolite Mineral Specimen Asturias Province Boal Spain
Location: Asturias Province, Boal, Spain
Weight: 1.3 Ounces
Dimensions: 2 Inches Long, 0.9 Inches Wide, 1.1 Inches Thick
The item pictured is the one you will receive.
Andalucite, a significant mineral in the geological and mineralogical fields, derives its name from Andalusia, a region in southern Spain where it was first identified and described. This aluminum nesosilicate mineral is characterized by its distinctive crystal structure and its formation under specific metamorphic conditions. Its presence in Spain, particularly in the Andalusian region, has been crucial for understanding its geological context and its role as an indicator mineral.
Andalucite is one of the three polymorphs of Al2SiO5, alongside kyanite and sillimanite. Although they share the same chemical formula, these minerals differ in their crystal structures, each stable under different pressure and temperature conditions. Andalucite usually forms in medium-grade metamorphic rocks and is commonly found in areas affected by regional metamorphism. Its occurrence helps geologists identify the specific pressure and temperature conditions present during the rock’s formation, making it an important indicator for studying metamorphic processes.
Andalucite belongs to the orthorhombic crystal system, which means its crystals have three axes that are all different lengths and meet at right angles. These crystals usually grow in prismatic shapes, often showing a square cross-section. The color of andalucite varies widely, including shades like pink, red, violet, brown, green, and sometimes no color at all. This color variety happens because tiny amounts of other elements get trapped inside the crystal. A special kind of andalucite called chiastolite displays a unique cross-shaped pattern made by dark carbon-rich spots within the lighter crystal. This pattern forms during crystal growth when impurities settle along certain directions inside the crystal structure.
