Helping San Diego, California and beyond since 1997.
Do you need
volunteer, community service, work, military or court hours?
|
|
Helping San Diego, California and beyond since 1997.
|
|
Click here and add this page to your favorites!
|
Encyclopedia Britannica - Main :: CHA-CHR |
|
|
CHLORITE , a group of green micaceous minerals which are hydrous silicates of aluminium, magnesium and ferrous iron. The name was given by A. G. ;Werner in 1798, from xXwpIric, " a green stone." Several species and many rather ill-defined varieties have been described, but they are difficult to recognize. Like the micas, the chlorites (or " hydromicas ") are monoclinic in crystallization and have a perfect cleavage parallel to the flat face of the scales and plates. The cleavage is, however, not quite so prominent as in the micas, and the cleavage flakes though pliable are not elastic. The chlorites usually occur as salt (H=23) scaly aggregates of a dark-green colour. They vary in specific gravity between 2.6 and 3o, according to the amount of iron present. Well-developed crystals are met with only in the species clinochlore and penninite; those of the former are six-sided plates and are optically biaxial, whilst those of the latter have the form of acute rhombohedra and are usually optically uniaxial. The species prochlorite and corundophilite also occur as more or less distinct six-sided plates. These four better crystallized species are grouped together by G. Tschermak as orthochlorites, the finely scaly and indistinctly fibrous forms being grouped by the same author as leptochlorites. Chemically, the chlorites are distinguished from the micas by the presence of a considerable amount of water (about 13%) and by not containing alkalis; from the soft, scaly, mineral
talc
magnesia
oxide
oxide
formula
Dana are daphnite, cronstedtite, thuringite, stilpnomelane, strigovite, diabantite, aphrosiderite, delessite and rumpfite.The chlorites usually occur as alteration products of other minerals, such as pyroxene, amphibole, biotite, garnet, &c., often occurring as pseudomorphs after these, or as earthy material filling cavities in igneous rocks composed of these minerals. Many altered igneous rocks owe their green colour to the presence of secondary chlorite. Chlorite is also an important constituent of many schistose rocks and phyllites, and of chlorite-schist it is the only essential constituent. Well-crystallized specimens of the species clinochlore are found with crystals of garnet in cavities in chlorite-schist at Achmatovsk near Zlatoust, in the Urals, and at the Ala valley near Turin, Piedmont; also as large plates at West Chester in Pennsylvania
Zermatt
Tirol
Closely allied to the chlorites is another group of micaceous minerals known as the vermiculites, which have resulted by the alteration of the micas, particularly biotite and phlogopite. The name is from the Latin vermiculor, " to breed worms," because when heated before the blowpipe these minerals ex-foliate into long worm-like threads. They have the same chemical constituents as the chlorites, but the composition is variable and indefinite, varying with that of the original
mineral
End of Article: CHLORITE If you wish, you can link directly to this article.
<a href="http://jcsm.org/StudyCenter/Encyclopedia/CHA_CHR/CHLORITE.html"> CHLORITE </a> |
|
|
(Previous) CHLORINE (symbol Cl, atomic weight 35`46 (0=16) |
(Next) CHLOROFORM (trichlor-methane), CHC13 |
|
Sponsored Advertisements