Search results
Results From The WOW.Com Content Network
Andalusite is a common metamorphic mineral which forms under low pressure and low to high temperatures. The minerals kyanite and sillimanite are polymorphs of andalusite, each occurring under different temperature-pressure regimes and are therefore rarely found together in the same rock. Because of this the three minerals are a useful tool to ...
Kyanite is the most stable at high pressure, andalusite is the most stable at lower temperature and pressure, and sillimanite is the most stable at higher temperature and lower pressure. [13] They are all equally stable at the triple point near 4.2 kbar and 530 °C (986 °F). [ 14 ]
Andalusite, kyanite, and sillimanite are the principal aluminium silicate minerals. [2] [3] [4] The triple point of the three polymorphs is located at a temperature of 500 °C (932 °F) and a pressure of 0.4 GPa (58,000 psi). These three minerals are commonly used as index minerals in metamorphic rocks.
An example is provided by the aluminium silicate minerals, kyanite, andalusite, and sillimanite. All three have the identical composition, Al 2 SiO 5. Kyanite is stable at surface conditions. However, at atmospheric pressure, kyanite transforms to andalusite at a temperature of about 190 °C (374 °F).
Chiastolite (/ k aɪ ˈ æ s t ə ˌ l aɪ t / ky-ASS-tə-lyte) [1] is a variety of the mineral andalusite with the chemical composition Al 2 SiO 5. It is noted for its distinctive cross-shaped black inclusions of graphite. The presence of these crosses caused the mineral to be used as a gem.
Chiastolite (variety of andalusite) Chlorastrolite (variety of pumpellyite-(Mg)) Chrysoprase (green nickel bearing chalcedony) Chrysotile (group name - asbestiform serpentine) Citrine (yellow variety of quartz) Cleveite (variety of uraninite) Clinochrysotile (polytype of chrysotile) Coltan (short for minerals of the columbite group)
The Si-O-M linkage between the silicates and the metals are strong, polar-covalent bonds. Silicate anions ([SiO 2+n] 2n−) are invariably colorless, or when crushed to a fine powder, white. The colors of silicate minerals arise from the metal component, commonly iron. In most silicate minerals, silicon is tetrahedral, being surrounded by four ...
A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. [1] The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram in Figure 1). [1]