minerals Flashcards
(340 cards)
is a manganoan variety of muscovite that was originally described in 1865 by J.F.H. Breithaupt who also named the mineral. The name alurgite is from the Greek word “halourges” meaning (“genuine purple dye from the sea”) in allusion to its typical reddish-purple color. Alurgite is a reddish-purple variety of muscovite that gets its color from the presence of Mn in its chemical formula. W. T. Schaller (1959) Placed alurgite as an intermediate between leucophyllite (now a synonym of aluminoceladonite) and muscovite.
Alurgite - K2(Mn, Mg,Al)4-5(Al,Si)8O20(OH)4
a common regional 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. All three polymorphs can be used as index minerals in metamorphic rocks. They all develop in alumina-rich pelites under different conditions of temperature and pressure. Andalusite form al low pressures (<1.5 Kb) and low moderate temperature in thermal aureoles and regional metamorphism of Buchan type (high T and low P). At higher temperature its invert in sillimanite.
Andalusite
commonly contains dark inclusions of carbon or clay which form a checker-board pattern when shown in cross-section, while viridine, or manganandalusite, is a Mn-rich variety of andalusite, with deep green colors.
variety chiastolite
a mineral belonging to the serpentine group of minerals. forms during low-grade metamorphism of olivine-rich rocks (peridotite and other ultrabasic rocks, gabbros, lamprophyres, etc.); is a major component in serpentinites. Antigorite can be accompanied by lizardite which can form the major component in pseudomorphs after orthopyroxene.
Antigorite
common component of some metamorphic and metasomatic rocks. Its name comes from the Latin word for clove and is an allusion to its typical and distinct clove-brown color.is the product of metamorphism of magnesium-rich rocks, especially ultrabasic igneous rocks and impure dolomitic shales. It also forms as a retrograde product rimming relict orthopyroxenes and olivine, and as an accessory mineral in cordierite-bearing gneisses and schists. also occurs as a retrograde metamorphic mineral derived from ultramafic rocks along with serpentinite.is formed by the breakdown of talc in ultramafic rocks in the presence of water and carbon dioxide as a prograde metamorphic reaction. The partial pressure of carbon dioxide (XCO2) in aqueous solution favors production of anthophyllite. indicative of at least greenschist facies metamorphism in the presence of carbon dioxide bearing metamorphic fluids.
Anthophyllite
occurs in contact and medium to high grade metamorphic rocks in association with garnet, cordierite, anthophyllite, cummingtonite, sapphirine, sillimanite,kyanite, quartz, staurolite and biotite. Gedrite was first described for an occurrence in Gèdres, Héas Valley, Francein 1836.
Gedrite
a solid solution between the end members Phlogopite KMg3AlSi3O10(OH)2 and Annite KFe3AlSi3O10(OH)2, although pure Annite does not occur in nature. In addition, small amounts of Na, Rb, Cs, and Ba may substitute for K, and like in other minerals, F can substitute for OH and increase the stability of Biotite to higher temperatures and pressures. a sheet silicate; iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called “iron mica” because it is more iron-rich than phlogopite. It is also sometimes called “black mica” as opposed to “white mica” (muscovite). the most ubiquitous ferromagnesian mineral occurring in most igneous and metamorphic rocks. Nearly pure phlogopite is found in hydrous ultrabasic rocks like kimberlite, and is also found in metamorphosed dolomites. ore Fe-rich compositions is common in dacitic, rhyolitic, and trachytic volcanic rocks, granitic plutonic rocks, and a wide variety of metamorphic rocks.
Biotite
Form: pseudoexagonal basal section (001), rectangular (110) section.
* Relief: Moderate.
* Color: brown to black.
* pleochroism: yellow to brown to green colors.
* Interference colors: third-order colors.
* cleavage: perfect {001} micaceous cleavage.
* extinction: Bird’s eye extinction, or bird’s eye maple, is a specific type of extinction exhibited by minerals of the mica group under cross polarized light of the petrographic microscope. It gives the mineral a pebbly appearance as it passes into extinction
Biotite
A fibrous variety of Brucite is called
nemalite
has a layer structure with hydroxyl (OH-) groups in hexagonal close packing. Each Mg is octahedrally coordinated to six O– groups and these octahedra share edges to form the layers. Brucite is a common alteration product of periclase, which is commonly formed in metamorphosed dolomites. common low-temperature hydrothermal mineral in metamorphosed limestones and chlorite schists and is often found serpentinized dunites.
Brucite - Mg(OH)2
Form: Is typically in flattened tabular crystals with rare rhombohedral terminations. Also found in lamellar and fibrous aggregates and as foliated masses.
* Cleavage: Perfect in one direction, basal.
* Relief: Moderate.
* Birefringence: High.
Brucite - Mg(OH)2
Aragonite will change to calcite at what temperature
380-470 °C
Trigonal carbonate have a structure similar to
halite
low pressure polymorph and is the only truly stable form under surface condition. Color: Colourless
* Form: In thin section usually show fine to coarse anhedral aggregate
* Cleavage: Perfect rhombohedral cleavage intersect at about 75°
* Interference colors: V orders interference colors
* Relief: Calcite is characterized by change in relief during a 360°rotation of the stage; the crystals is said to “twinkle” during rotation.
Calcite
tin oxide mineral and it is the most important source of tin, and most of the world’s supply of tin is obtained by mining cassiterite. Small amounts of primary cassiterite are found in igneous and metamorphic rocks throughout the world. It is also a residual mineral found in soils and sediments. more resistant to weathering than many other minerals, and that causes it to be concentrated in stream and shoreline sediments an be found in hydrothermal veins and pegmatites associated with granite intrusions. May also precipitate from volcanic gas, as shown by experiments of Africano et al. (2002), in which it deposits in the 550-240°C range.
Cassiterite - SnO2
Form: Usually as fibrous, botryoidal crusts or concretionary masses. Granular, coarse to fine.
* Twinning: Both contact and penetration twins.
* Colour: Black, yellow, brown, red or white.
* Relief: Very High.
* Interference colours: Very High.
Cassiterite - SnO2
“the lilac miracle of Siberia” and It is considered “the main mineralogical discovery of the second half of the 20th century”. Charoite was discovered in 1949 and confirmed as a new mineral species in 1977. According to the discoverers of the mineral, the name originates from the Chara River, situated close to the southem border of the Murun complex. An “unofficial” hypothesis suggests the Russian word “charovat” (to charm) as a possible origin for the name. It has been found at only one locality in at the broad contact aureole of the Early Cretaceous Malyy Murun syenite massif, northwestern Aldan Shield of the Siberian Craton
Charoite - K5Ca8(Si6O15)2(Si2O7)Si4O9(OH)*3(H2O)
- Form: Massive to Fibrous.
- Color: Colorless.
- Pleochroism: Weak (from rose to colorless).
- Relief: Low.
- Interference colors: Low (I order white-gray).
Charoite - K5Ca8(Si6O15)2(Si2O7)Si4O9(OH)*3(H2O)
ostly monoclinic (also triclinic or orthorhombic) micaceous phyllosilicate minerals with a structure consisting of T-O-T layers with two layers having their silicate tetrahedral apices pointing towards each other, separated by an interlayer that may be simple octahedrally coordinated cations or which may be a brucite-like layer of two sheets of closely packed OH groups with the interstices between sheets providing the octahedral cordination site. linochlore: (Mg5Al)(AlSi3)O10(OH)8
♦ Chamosite: (Fe5Al)(AlSi3)O10(OH)8
♦ Nimite: (Ni5Al)(AlSi3)O10(OH)8
♦ Pennantite: (Mn,Al)6(Si,Al)4O10(OH)8 an important constituent of many contact and regional metamorphic rocks of low to medium grade, usually with temperatures of to 400°C and pressures up to a few Kb. It also found in amygdules, fractures in altered volcanic rocks, hydrothermal vein deposits and soils often found with biotite, garnet, staurolite, andalusite, muscovite, chloritoid, and cordierite in pelitic rocks. In mafic rocks, it occurs with talc, serpentine, actinolite, hornblende, epidote, and garnet. It can also be found with feldspars, quartz, calcite, dolomite, olivine, plagioclase, rutile, ilmenite, titanite, magnetite, chromite, sulfides, zircon, and zeolites. forms by the alteration of mafic minerals such as pyroxenes, amphiboles, biotite, staurolite, cordierite, garnet, and chloritoid. Chlorite can also occur as a result of hydrothermal alteration of any rock type, where recrystallization of clay minerals or alteration of mafic minerals produce
Chlorite - (Mg,Fe2+,Fe3+,Mn,Al)12(Si,Al)8O2016
- Color: Colourless ore green, pale green
- Habit: Tabular crystals with pseudo-hexagonal shape
- Cleavage: (001) perfect
- Interference colors: Very weak (brown, deep green, gray), usually with anomalous deep berlin blue
- Relief: Low to moderate
Chlorite - (Mg,Fe2+,Fe3+,Mn,Al)12(Si,Al)8O2016
formely known as octahedrite
polymorph of titanium dioxide
anatase
formed by weathering pf titanite
anatase
weathered anatase becomes
rutile
