With a 0.007-0.011 birefringence and dispersion is about 0.016, precious beads andalusite is a pretty and unusual natural gemstone. It is composed by aluminum silicate. Coming from the class of silicates with isolated silica units, precious beads andalusite has an orthorhombic crystal system. It is named after Andalucia, southern Spain, where it was discovered. Many precious beads andalusites display different colors within the same stone-the result of its strong pleochroism. It is one of three polymorphs of aluminum silicate, the other two being sillimante and kyanite. Each is formed under different pressure and temperature conditions. The color of precious beads andalusite is available in brown, green, yellow, pink and violet.
Cuts with a long axis (in particular, oval, marquis, or emerald cuts) often show one color near the center and a second (usually darker) color towards the ends. Square and round cuts frequently blend the colors into a mosaic effect. The habit of precious beads andalusite is nearly square, columnar crystals, or massive. The most common faceted cuts are brilliants and baguettes. A translucent to opaque variety of precious beads andalusite known as chiastolite contains dark inclusions in a cruciform arrangement. The cleavage is distinct in one direction. These are cut and polished for use as amulets in many countries, largely because of the symbolism of the cross. Despite being attractive, hard, and tough enough for high-quality jewelry, precious beads andalusite is still comparatively unknown with refractive index between 1.634-1.648 and specific gravity’s range in 3.15-3.17. As a result, even clean gems with good color are not expensive, custom cuts and gems of precious beads andalusite that contain exceptional inclusions tend to be more valuable. The hardness is 7.5.
Precious beads andalusite is an aluminum silicate mineral that occurs in relatively small quantities in various metamorphic rocks, specifically in altered sediments. It is found extensively in the Inyo Mountains, Mono County, California, in the USA, in Kazakhstan, and in South Africa. Other sources of precious beads andalusite are Sri Lanka, Spain, Brazil Myanmar, China, and Russia (Ural Mountains). Most specimens contain inclusions of some description, the most common being needles of rutile. There is a massive bright green variety called viridine (from Arizona) that is colored by manganese. Precious beads andalusite has vitreous luster and splintery fracture.
