Listing
Description:
Magnesite
is magnesium carbonate, MgCO3. Iron (as Fe2+)
substitutes for magnesium (Mg) with a complete solution series with siderite, FeCO3.
Calcium, manganese, cobalt, and nickel may also
occur in small amounts. Dolomite, (Mg,Ca)CO3, is almost indistinguishable from magnesite
Detailed Description:
Magnesite occurs as veins in and
an alteration product of ultramafic rocks, serpentinite
and other magnesium rich rock types in both contact and regional metamorphic
terranes.
These magnesites often are cryptocrystalline and contain silica as opal or chert.
Magnesite is also present within
the regolith
above ultramafic rocks as a secondary carbonate within soil and subsoil, where
it is deposited as a consequence of dissolution of magnesium-bearing minerals
by carbon dioxide within groundwaters.
Formation
Magnesite can be formed via talc
carbonate metasomatism of peridotite
and other ultrabasic rocks. Magnesite is formed via carbonation of olivine in the
presence of water and carbon dioxide, and is favored at moderate temperatures
and pressures typical of greenschist facies;
Magnesite can also be formed via
the carbonation of magnesian serpentine
(lizardite) via the following reaction:
Serpentine + carbon dioxide → Talc + magnesite + Water
Serpentine + carbon dioxide → Talc + magnesite + Water
2Mg3Si2O5(OH)4
+ 3CO2 → Mg3Si4O10(OH)2
+ 3MgCO3 + H2O
Forsterite
magnesia-rich olivine
compositions favor production of magnesite from peridotite. Fayalitic
(iron-rich) olivine favors production of magnetite-magnesite-silica
compositions.
Magnesite can also be formed
from metasomatism in skarn
deposits, in dolomitic
limestones,
associated with wollastonite, periclase,
and talc.
Magnesite is also found in a
number of Precambrian carbonate hosted sediments, and is thought to have formed
as an evaporite.
Uses
Magnesite can be used as a slag former in
steelmaking furnaces, in conjunction with lime,
to protect the magnesium oxide lining. It can also be used as a
catalyst and filler in the production of synthetic rubber and in the
preparation of magnesium chemicals and fertilizers.
Similar to the production of
lime, magnesite can be burned in the presence of charcoal to produce MgO,
otherwise known as periclase. Such periclase is an important product in
refractory materials.
Magnesite can also be used as a
binder in flooring material.
In fire assay, magnesite cupels
can be used for cupellation as the magnesite cupel will resist the high
temperatures involved.
It is dyed to make beads, as is howlite.
PRICE
$2.42/kg
or $1.1/ib
For more information:
mobile: +2348039721941
contact person: emeaba uche
e-mail: emeabau@yahoo.com
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