Andalusite, a captivating but uncommon gemstone, is known for its distinctive crystal structure and color variations. Here’s a breakdown of its key characteristics:

Rarity and Color:

• Andalusite is a rare gem, typically found in a bright brownish-yellow color.

Crystal Structure:

• The crystal form plays a crucial role in identifying Andalusite.
• While the base structure is complex, many crystals have a unique feature: their pointed shape softens towards the top, forming a flat surface.

Natural Cracks and Color Patterns:

• Andalusite often exhibits natural cracks along two axes, creating a layered appearance.
• These cracks reveal distinct yellow-brown color patterns, another key identifier.
• Interestingly, different color tones related to yellow-brown can be observed along different axes within the same crystal.

Chiastolite Variety:

• A unique type of Andalusite called Chiastolite features inclusions of black graphite within the crystal.
• These inclusions form a cross-like pattern or intersecting lines, making Chiastolite highly recognizable.

Transparency and Light Effects:

• Due to natural cracks, Andalusite is usually semi-transparent or translucent.
• Very rarely, transparent gem-quality crystals exist, showcasing color variations and subtle light diffraction when cut and polished.

Crystal Formation:

• Andalusite occurs as single crystals, crystal groups, or clusters.
• Twinned crystals, where two crystals grow together, are more common than perfect single crystals.

Chemical Composition:

• Primarily composed of Aluminum, Silicon, and Oxygen. Trace elements can introduce colors like pink, orange, purple, and yellow.

Physical Properties:

• Andalusite belongs to the orthorhombic crystal system.
• It boasts a hardness of 7.5 on Mohs scale.
• With a specific gravity of 3.0 to 3.2, it’s a relatively lightweight gemstone.
• The refractive index ranges from 1.64 to 1.648.

Origin and Location:

• First discovered in the Andalusia region of Spain.
• Found in countries like Belgium, Australia, and Russia.
• In Sri Lanka, it’s known as “Gini Boku Thora” and is reported from areas like Ginigathena and Nawalapitiya.

Important Note:

• Andalusite can be mistaken for Alexandrite due to dichroism (color change with viewing angle).
• Its strong absorption lines at specific wavelengths (5505, 5475, and 5535 nanometers) can aid in proper identification.

Remember: Andalusite’s unique crystal form, color variations, and rarity make it a fascinating gem for collectors, even though its natural flaws limit its use in everyday jewelry.