Carbonates: Magnesite
Diagnostic card.
on the picture. Crystals of magnesite, associated with quartz.
Mg CO 3
The trigonial trigonometric system
Hardness 4-4,5
Specific weight 3
Cleavage is perfect
Cracked shell
Color is colorless, differently colored
Color in powder white
Glitter glass
Magnesite is a bitter spar (not to be confused with dolomite, also sometimes called bitter spar), magnesium carbonate. Glitter is glassy or dull. Transparent to translucent. Colors: white, yellowish, brownish, gray. The line is white. Fracture shell. It's fragile. Cleavage is perfect.
Occurs in hydrothermal deposits or develops as a product of weathering of ultrabasic rocks. Crystals (trigonal syngony) are rhomboid or columnar. Aggregates from thin to coarse-grained, sparse, shpatopodobnye. Serves for the production of refractory bricks. Places of distribution: Austria, Czech Republic, Greece, CIS, USA.
Magnesite belongs to the calcite group and also crystallizes in trigonal symmetry. Crystals of magnesite are simpler and less rich in a variety of forms compared with calcite. In appearance, these are mostly rhombohedra, sometimes short prisms or pseudoblocks, sometimes with distinct hexagonal contours. Crystals of magnesite are rare in nature. More often this mineral is present in the form of dense masses. Their color is grayish-white to light gray. The magnesite masses are opaque, have a typical porcelain appearance and a shell fracture. Sometimes they may have a loose earthy structure or be microcrystalline granular aggregations. Magnesite can also contain other elements that sometimes partially replace magnesium. Among them, iron is particularly noteworthy, the presence of which determines the appearance of such varieties as broiderite and mesithite, whose crystals are colored in yellowish and brown tones.
Diagnostic signs.
Some samples under the influence of ultraviolet rays show a bluish or greenish fluorescence. With dilute acids, magnesite reacts without effervescence, and this distinguishes it from calcite.
Origin.
Magnesite - a mineral is very common, which is formed in a variety of geological conditions. Large masses of magnesite are formed during the weathering of rocks enriched in magnesium (peridotites and serpentinites). They are also partially formed during the transformation of sedimentary rocks (dolomites, limestones) under the action of waters rich in magnesium. Magnesite is found in hydrothermal veins and in some pegmatites.
Place of Birth.
In Italy, well-known table and hexagonal crystals, combined in beautiful brownish-yellow aggregates, covered with quartz crystals and called "Dosso dei Crystalli" ("crystal spin") in Val Malenko (Lombardy region). Massive magnesite is mined industrially in the regions of Piedmont, Alto Adige and Tuscany. Outside Italy, significant deposits of massive magnesite, where beautiful crystals are found, are located amongst others in Styria (Austria), Silesia (Poland) and on the island of Euboea (Greece).
Application.
Magnesite is of great importance for the production of widely used refractories. In addition, it is the most important mineral raw material for the production of metallic magnesium and its salts, which, firstly, are used to make alloys, and secondly, they are used in medicine, as well as in the building materials industry for the production of certain types of cement.
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