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An example of the tetragonal crystals, wulfenite Two different views (top down and from the side) of the unit cell of tP30-CrFe (σ-phase Frank–Kasper structure) that show its different side lengths, making this structure a member of the tetragonal crystal system. In crystallography, the tetragonal crystal system is one of the 7 crystal systems.
Media in category "Tetragonal minerals" This category contains only the following file. Cassiterite.jpg 5,616 × 3,744; 4.17 MB
Optical properties of common minerals Name Crystal system Indicatrix Optical sign Birefringence Color in plain polars Anorthite: Triclinic: Biaxial (-) 0.013
Tetragonal crystal system (3 C, 1 P) Pages in category "Tetragonal crystals" The following 2 pages are in this category, out of 2 total.
It crystallizes in the tetragonal system, in the form of square tabular crystals, and with distinct cleavage on {011}. It crystals also display transparency and adamantine luster. The X-ray diffraction data, calculated cell dimensions, constants and optic axial angles of the synthetic wulfenite are consistent with those of the natural mineral.
Crystal systems that have space groups assigned to a common lattice system are combined into a crystal family. The seven crystal systems are triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. Informally, two crystals are in the same crystal system if they have similar symmetries (though there are many exceptions).
The steeper angle gives anatase crystals a longer vertical axis and skinnier appearance than rutile. Additional important differences exist between the physical characters of anatase and rutile. For example, anatase is less hard (5.5–6 vs. 6–6.5 on the Mohs scale) and less dense (specific gravity about 3.9 vs. 4.2
It is also known to occur as small grains in detrital sands. Crystals are rare, but when found can produce nicely shaped short prismatic crystals with pyramidal terminations. It is commonly associated with zircon, monazite, gadolinite, fergusonite, uraninite, yttrialite and pyrochlore. [4] Thorite is currently an important ore of uranium.