Topaz - Ougyoku

Al ₂ F ₂ SiO ₄ . Also known as topaz. Orthorhombic crystal system, space group Pbnm , lattice constants a ₀ = 0.465, b ₀ = 0.880, c ₀ = 0.840 nm. There are four basic elements in the unit cell. Hardness 8. Density 3.49-3.57 g cm ^-3 . A transparent mineral with colorless striations and a vitreous luster. It is colorless to yellow, and is used as a gemstone. Note that the product name topaz also includes citrine, which has a hardness of 7, so be careful.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Al₂F₂SiO₄．トパーズともいう．斜方晶系，空間群Pbnm，格子定数 a₀ ＝ 0.465，b₀ ＝ 0.880，c₀ ＝ 0.840 nm．単位胞中に4個の基本組成が入る．硬度8．密度3.49～3.57 g cm^－3．無色の条痕，ガラス光沢の透明な鉱物．色は無色ないし黄色で，宝石として利用される．なお，商品名としてのトパーズには，硬度7の黄水晶もあるので要注意．

出典　森北出版「化学辞典（第2版）」化学辞典 第2版について　情報