Greenalite
Encyclopedia
Greenalite is a mineral
in the kaolinite
-serpentine group with the chemical composition (Fe2+,Fe3+)2-3Si2O5OH4. Occurs as a primary phase in banded iron formation
s. Rocks which contain greenalite are usually bright green, pale green or pale brown. Greenalite occurs with quartz
, stilpnomelane
, siderite
, chamosite
, pyrite
and minnesotaite. It is commonly oolitic
.
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
in the kaolinite
Kaolinite
Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra...
-serpentine group with the chemical composition (Fe2+,Fe3+)2-3Si2O5OH4. Occurs as a primary phase in banded iron formation
Banded iron formation
Banded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...
s. Rocks which contain greenalite are usually bright green, pale green or pale brown. Greenalite occurs with quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, stilpnomelane
Stilpnomelane
Stilpnomelane is a phyllosilicate mineral of the mica group. It has the formula K81227.Stilpnomelane occurs associated with banded iron formations. It is a metamorphic mineral associated with the blueschist and greenschist facies....
, siderite
Siderite
Siderite is a mineral composed of iron carbonate FeCO3. It takes its name from the Greek word σίδηρος sideros, “iron”. It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus...
, chamosite
Chamosite
Chamosite is the Fe2+end member of the chlorite group. A hydrous aluminium silicate of iron, which is produced in an environment of low to moderate grade of metamorphosed iron deposits, as gray or black crystals in oolitic iron ore. Like other chlorites, it is a product of the hydrothermal...
, pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
and minnesotaite. It is commonly oolitic
Oolite
Oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic word òoion for egg. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks composed of ooids larger than 2 mm are called pisolites...
.