Magnesite
Magnesium
Carbonate
MgCO3
Magnesium is the eighth most abundant element in the Earth's crust
and can be found in 60 different minerals.
The
Present Scenario
Notable Occurrences are Austria; Bahia, Brazil; Korea; China;
California, USA and many European localities.
Magnesite
does not ordinarily form good crystals, but can make up a substantial
portion of some rock types. It forms commonly from the alteration of
magnesium-rich rocks during low grade metamorphism while they are in
contact with carbonate-rich solutions. Magnesite has the same crystal
structure of calcite, hence its inclusion into the calcite mineral
group. Many of the properties of magnesite are either identical or
similar to those of calcite. However, the magnesium ion does not allow
the carbonate ion (CO3) to interact as easily with cold
acids, as the calcium ion does in calcite. This provides the best
means of distinguishing magnesite from calcite. However,
dolomite(MgCa(CO3)2) can be almost
indistinguishable from magnesite.
Physical Characteristics
- Color
is white or gray, also tinted yellow or brown.
- Luster
is vitreous.
- Transparency
crystals are translucent to transparent only in individual crystals.
- Crystal
System is trigonal; bar 3 2/m
- Crystal
Habits are usually massive forms such as lamellar, fiberous and
course to fine grained rocks. Crystals are extremely rare, but when
found are in the form of rhombohedrons or hexagonal prisms with a
pinacoid termination.
- Cleavage
is perfect in three directions forming rhombohedrons.
- Fracture
is conchoidal to uneven.
- Hardness
is 4 - 4.5.
- Specific
Gravity is approximately 3.0 (average)
- Streak
is white.
- Associated
Minerals calcite, dolomite, aragonite, strontianite and serpentine.
- Other
Characteristics: effervesces easily only in hot dilute hydrochloric
acid.
- Notable
Occurrences include Austria; Bahia, Brazil; Korea; China;
California, USA and many European localities.
- Best
Field Indicators are crystal habit, reaction to acid, occurrence and
cleavage.
Uses
- Dead-burned
magnesia - DBM Sinter magnesia
Basic refractories
- Fused
or electrofused magnesia - FM
Thermal insulation (refractories)
Electrical insulation (electric ovens and appliances)
- Caustic-calcined
magnesia - CCM
Extraction of magnesium
Production of fused magnesia
Cement, Insulation
Paper
Fertilizer and animal feed
Stabilizer during vulcanization of rubber
Production of uranium
Chemical and environmental applications (notably in water treatment
and gas desulfurization)
- Magnesite
or magnesium carbonate (precipitated)
Insulation, Rubber
Paint pigments and Ink
Glass and ceramics
Chemistry
- Brucite
or magnesium hydroxide
Sugar refining
Flame and smoke retardants
Chemical and environmental applications (notably in water
treatment)
Pharmaceuticals
- Magnesium
chloride
Cement
Ceramics and refractories
Textiles, Paper
Chemical applications
Production of magnesium
- Magnesium
sulfate
Pulp and paper
Animal feed
Pharmaceuticals
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