Topaz can come in a variety of colors, including light blue.
All crystals and stones are made up of a combination of chemicals that bind together into a solid object. Understanding the composition of stones, such as the November birthstone, topaz, is important if you want to know why it is a certain color, how hard it is or how it is formed.
Chemical Composition
The chemical composition of the November birthstone topaz is Al2[F2/SiO4]OHCrFeMn. This indicates that it is mainly made of aluminum, but there is also silicon, fluorine, oxygen, hydrogen, chromium, iron and manganese present.
Chemical Classification
The chemical composition of topaz places it in the silicate family. More specifically it is part of the nesosilicate division of the silicate family. Silicates are the largest class of minerals found on the planet. A third of all minerals found are part of the silicate group. This is because oxygen and silicon are the most abundant elements found on Earth. Nesosilicates are minerals that have single tetrahedrons that form without attaching to other clusters. Garnet, kyanite, olivine and howlite are some other nesosilicate family members.
Colors
The color of any stone is due to its chemical composition. The varying colors of topaz are a result of additional metals that mix with the stone as it is forming. Dark to golden-yellow topaz is common. You can also find white, silver, blue, green and pink versions. It is not uncommon to find clear or colorless topaz as well.
Crystallization
Topaz forms in an orthorhombic crystal prism. Orthorhombic refers to a crystallization formation that has 90 degree angles but has three unequal axes. Topaz forms in tall rectangular formations with a tall height, medium width, and short to medium depth. Sulfur, Barite, Chrysoberyl and Celestite are other types of crystals that form in the same orthorhombic manner as topaz.
Hardness
Like other stones and crystals, topaz is measured on the Mohs scale for hardness. The scale has a range from 1 to 10, with 1 being very easy to scratch the surface and 10 being a diamond which cannot be scratched at all. Topaz registers as an 8 on this scale, which makes it a relatively hard birthstone.
Tags: chemical composition, minerals found, silicate family, that form, Topaz forms