Spinel (oxides): manganites
Diagnostic Card.
On the picture. Crystals gahnite black found in Charlemont, Massachusetts.
Zn Al 2 O 4
Crystal system cubic
Hardness of 7.5-8
Specific gravity 4.6
Cleavage is absent
fracture conchoidal
Color changeable
Color gray powder
Gloss glass
The mineral is black (a kind automolit), and greenish-black, blue and rarely yellow or brown. It forms beautiful crystals octahedral shape.
Diagnostic features.
It can be confused with the minerals of the same color and the crystallographic form. Among them, only attracts iron magnetite.
Origin.
Most often found in alluvial placer deposits of precious stones. In addition, present in ores and zinc deposits in the zones of contact metamorphism, and some limestones.
Place of Birth.
It is found in Sweden (Falun Riddarhyuttan), in the United States (Franklin and Sterling Hill, New Jersey), Brazil and elsewhere. In Italy, there is first and foremost in Tirol, near the city of Catanzaro, in the form of beautiful blue crystals. In addition, it found in Midzhiandone about ornavasso in Wald Toce, which represented black octahedral crystals.
Manganites. Eliseevka, Azov, Ukraine. Grain with koronitovoy trimmed muscovite. ~ 10x12 cm Photo:. © AA Evseev.
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Toxic and hazardous radioactive rocks and minerals
** - Poisonous stones and minerals (obligatory check in chemical laboratory + clear indication of toxicity)
** - Radioactive rocks and minerals (obligatory check on a regular dosimeter + ban on the open sale of radioactivity in the event of more than 24 mR / hour + additional measures to protect the population)
Catalog minerals and gems in groups of the world
** - Poisonous stones and minerals
** - Radioactive rocks and minerals
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