Spinell () is the magnesium-aluminium member of the major spinel group of mineral. Balas ruby is an old name for a pink spinel. Spinels crystallize in the geometric system; standard crystalline shapes are octahedrons, mostly twins. There' s a uniquely beautiful naturally occurring whitish spinel that has now been forgotten and briefly appeared in present-day Sri Lanka.
A number of Spinels are among the most renowned gems, including the Black Prince Ruby and the Timur Ruby in the crown jewelry of Britain and the Côte de Bretagne, formerly from the crown jewelry of France. Samaritan Spinel is the biggest known spinel in the worid and weighs 500 ct. (100 g).
They have been known as spinel ruby or ballas ruby. Before the advent of contemporary sciences, spinel and ruby were both known as ruby. In the eighteenth and nineteenth centuries the term ruby was only used for the type of gemstone used in the stone aluminium oxide and the term spinel was used.
Mining in Gorno Badakhshan county in Tajikistan has been the primary resource for hundreds of years for scarlet and rose spinel. Spinell was long time found in the precious stone containing pebbles of Sri Lanka and in limestone of the province Badakshan in today's Afghanistan and Tajikistan as well as in Mogok in Burma. Lately, precious stone spinel have also been found in the murmurs of Luc Yen (Vietnam), Mahenge and Matombo (Tanzania), Tsavo (Kenya) and in the pebbles of Tunduru (Tanzania) and Ilakaka (Madagascar).
Spinell occurs as a metamorphous rock, but also as a prime rock in a few eruptive mafia rock types; in these rock types the magma is relatively weakly alkaline compared to aluminum, and aluminum oxides can be formed as minerals alumina or bond with magnesium to spinel. That is why spinel and ruby often occur together.
Spinel pyrogenesis in magnetic tissues is widely discussed, but certainly results from the interactions with further developed magma or tissues (e.g. gobro, troctolite). Spinel, (Mg,Fe)(Al,Cr)2O4, occurs in the topmost earth layer in pearidotite, between approx. 20 km and approx. 120 km, down to the depth, according to chrome concentration.
6 ] At significantly lower grades, above the Moho, calculated plainclase is the more stabilised alumina rock in pearidotite, while the more stabilised layer of the shell is below the spinel stabilisation range. Spinel, (Mg,Fe)Al2O4, is a frequent inorganic in the Ca-Al-rich inclusion (CAIs) of some chondrite meteors. "Spinell minerals."
"Cr's effect on the grenade-spinel junction in the Earth's mantle: Jeopardy up ^ "Researchers find application for viscous spinel ceramics". Transparent Armor from NRL ; Spinel Could Also Rugedize Your Smart Phone". Gems of the World 3. issue, Stereo, pp. 116-117. The Wikimedia Commons has a relationship to Spinel.