Along with the more common rutile and brookite, anatase is one of the three forms of titanium dioxide. The mineral is usually only sold in its natural form to collectors, but faceted stones are very occasionally also encountered in sizes below one carat. While most crystals are actually brownish or blue, the majority are sufficiently dark in tone so as to appear almost black.
The mineral was named in 1801 after the Greek word for “extension”, as its crystals are longer than those associated with its polymorph, rutile. The two minerals can also be differentiated by anatase’s lower measurable hardness (5.5-6.0) and density, as well as its distinctive sub-metallic lustre. However, when heated to temperatures in excess of 915 degrees Celsius, anatase transforms into the more stable rutile.
Characteristics of Anatase
- Hardness: 5.5 -6
- Transparency: Transparent, Translucent
- Chemical composition of [gemstone]
- Tenacity: Brittle
- Crystal system: Tetragonal