![]() ![]() In some cases, the impurity of quartz linked to these cations can produce colored varieties of quartz (e.g. Quartz is commonly almost purely SiO 2, but it may accommodate some cations in traces like Al 3+, Na +, Li +, K +, Ti 4+, and Fe 3+. In left-handed quartz this rotation is anticlockwise. Right-handed quartz has a virtual helix of SiO 4 tetrahedrons that rotates clockwise with respect to the long-axis (c-axis). α-quartz is a chiral substance with crystal class 32 and, therefore, can exist in two forms: right-handed quartz and left-handed quartz. The α-β transformation, indeed, involves no atom exchange or breaking of bonds and occurs very easily in nature. The structure of α-quartz is trigonal and characterized by a slight rotation of the SiO 4 tetrahedrons with respect to the β-quartz structure. β-quartz has an hexagonal crystal lattice with ‘rings’ of 6 SiO 4 tetrahedrons linked to each other. There are two forms of quartz: α-quartz, stable below 573 ☌ at ambient pressure, and β-quartz, stable from 573 to 870 ☌. Quartz is a framework silicate and one of the naturally occurring polymorphs of SiO 2. The name ‘quartz’ likely derives from the Saxon word ‘ Querkluftertz’ (cross-vein ore), since it is also a common mineral in veins and metasomatic rocks. Quartz is a common rock-forming minerals that occurs in most acid and intermediate igneous rocks, in many metamorphic rocks, and in terrigenous sedimentary rocks. Quartz is the most common crystalline form of silica dioxide (SiO 2) and the second most abundant mineral in the Earth’s crust after feldspars.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |