Topaz in Fashion Jewelry Topaz remains a method of fluorine aluminosilicate. Chemically, the arrangement of topaz canister remain embodied through the formulary Al2SiO4 (F, OH) 2. Topaz crystals are generally prismatic and end in pyramidal or other faces. Topaz crystals often have a well-developed basal cleft. Cutting and polishing crystals like gemstones requires special care.