BARITE [ Sulfates : Barite ] - Jejaring Kimia


Juli 14, 2011

BARITE [ Sulfates : Barite ]

BaSO4, barium Sulfate
Barite is a common mineral and makes very attractive specimens. It often is an accessory mineral to other minerals and can make a nice backdrop to brightly coloured crystals. At times bladed or tabular crystals of Barite form a concentric pattern of increasingly larger crystals outward. This has the appearance of a flower and when coloured red by iron stains, these formations are called "Desert Roses". Because Barite is so common, it can be confused for other minerals. Celestite (SrSO4) has the same structure as barite and forms very similar crystals. The two are indistinguishable by ordinary methods, but a flame test can distinguish them.
By scrapping the dust of the crystals into a gas flame the colour of the flame will confirm the identity of the crystal. If the flame is a pale green it is barite, but if the flame is red it is celestite. The flame test works because the elements barium (Ba) and strontium (Sr) react in the flame and produce those colours.

Physical Characteristics

Colour: variable but is commonly found colourless or white, also blue, green, yellow and red shades
Luster: vitreous
Transparency: crystals are transparent to translucent
Crystal System: orthorhombic; 2/m 2/m 2/m Crystal Habits: include the bladed crystals that are dominated by two large pinacoid faces top and bottom and small prism faces forming a jutting angle on every side. There are many variations of these faces but the flattened blades and tabular crystals are the most common. If the pinacoid faces become diminished or are absent, the resulting prismatic crystal has a rhombic cross section. Also scaly, lamellar, and even fiberous
Cleavage: perfect in one direction, less so in another direction
Fracture: conchoidal
Hardness: 3 - 3.5
Specific Gravity: approx. 4.5 (heavy for translucent minerals)
Streak: white
Other: green colour in flame test (see above)
Associated Minerals: numerous but significant associations have been with chalcopyrite, calcite, aragonite, sulfur, pyrite, quartz, vanadinite, cerussite and fluorite among many others
Major Occurrences: include Oklahoma, Connecticut and Colorado, USA; England and Germany
Best Indicators: crystal habit, flame test and density

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Jejaring Kimia Updated at: Juli 14, 2011

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