Silicates: Staurolite
Diagnostic card.
In the photo there is a double of staurolite in the form of Andreevsky cross (France). Above: prismatic crystal of staurolite (Pizzo Forno, Canton of Ticino, Switzerland).
Fe 2 Al 9 Si 4 O 22 (OH) 2
Diamond orthogonality
Hardness 7-7,5
Specific weight 3.65-3.83
Cleavage is difficult to manifest
Crack irregular
Color brown-red, dark gray
Color in powder white
Gloss from glass to resin
The mineral crystallizes in a rhombic syngony, its crystals are prismatic, more or less elongated. Coloring from brownish-red to dark-gray; Crystals are almost opaque, sometimes translucent; Shine from glass to resin. Surfaces are uneven, covered with a touch of products of secondary changes. Often there are twins in the form of a Greek or St. Andrew's cross (with angles of 120 and 60 o ). Staurolite is fragile; On cleavage is divided with great difficulty, but it easily breaks perpendicularly to elongation.
Staurolite is a silicate of aluminum and iron, an unusual mineral that forms splices of crystals resembling a cross in shape. This feature is reflected in the name of the stone (Greek stauros - "cross", lithos - "stone"), which gave him in 1792 the French scientist JC Delametri. Otherwise staurolites are called crest stones.
This interesting mineral is often found among mica schists. Usually the size of the little finger, about 7 cm, it slightly narrows from both ends. At the site of the fault clearly visible white cross in the frame of black veins that make up the second cross. Thus, it is impossible to meet two identical square crosses, and after polishing an interesting stone appears, known to the ancients, called lapis crusifer, a stone-cross.
Chemical composition-content (in%): FeO-15.8; Al2O3 -55.9; SiO2 = 26.3; H2O -2; Admixtures of manganese (normarkarkit), cobalt (lyusakite), magnesium, calcium, titanium are noted. Cleavage is perfect by (010) and (100), imperfect by (110). Color reddish-brown, brown, black, rarely dark blue (lusakit).
Diagnostic signs.
Staurolite is refractory, does not lend itself to the action of acids. Partially decomposed in sulfuric acid.
Origin.
Typical conditions for the formation of staurolite are associated with medium-temperature metamorphism. It is often associated with paragonite, kyanite and garnet. Less commonly formed when pegmatites are formed or in contact metamorphism. Being very hard, staurolite is often found in alluvial deposits.
Place of Birth.
The whole world has become famous for its elongated prismatic crystals of staurolite, light red and translucent, from Pizzo Forno (Canton Ticino, Switzerland), where they are distributed along with blue kyanite and paragonite in mica shales. Crystals of impressive sizes came from Moravia (Czech Republic), Bavaria, Loch Ness (Scotland) and the state of Minas Gerais (Brazil). In the states of Georgia and New Mexico (USA) and in Morbihan (the peninsula of Brittany, France) cruciform doubles of staurolite were found. Staurolites are widely distributed in Russia on the territory of the Kola Peninsula and the Southern Urals. Stavrolite deposits also exist in France, Germany, Austria and some other countries of the world.
Staurolite is a silicate of aluminum and iron. The glitter is glassy, dim. Transparent to translucent. Color reddish-brown. The line is white. The fracture is conchoidal, steep-dense, uneven. Cleavage is perfect. Regular splices with a kyanite are frequent. Crystals (rhombic syngony) usually form cruciform twins. Distribution: Spessart (Germany), Tyrol (Austria), Tessin (Switzerland), USA.
- Ghetchellit - "New Almaden blend" - arsenide and antimony sulfide (modern sulfosol)
- Antimony is a toxic metal (semimetal) , widely used in metallurgy, medicine and engineering
- Zirconium - a rare and undiscovered metal and the most dangerous precious stone in oxide and salt
- Gold - yellow dangerous and poisonous metal of modern accurate digital and cable technologies
- Sulfur is a golden-yellow toxic substance and a sign of active volcanic activity
- Cadmium is an undisputed toxic silvery metal unknown to a wide range of people
- Lead - a toxic gray imitator of metallic silver and toxic metal blende
- Arsenic is a classic poison of medieval and modern poisoners and medicine in medicine
Poisonous and radioactive dangerous stones and minerals
** - poisonous stones and minerals (mandatory check in the chemical laboratory + explicit indication of toxicity)
** - radioactive stones and minerals (mandatory check on the standard dosimeter + ban on open sales in case of radioactivity exceeding 24 milli / g / h + additional measures of population protection)
Catalog of minerals and semi-precious stones of the world by groups
** - poisonous stones and minerals
** - radioactive stones and minerals
Comments
When commenting on, remember that the content and tone of your message can hurt the feelings of real people, show respect and tolerance to your interlocutors even if you do not share their opinion, your behavior in the conditions of freedom of expression and anonymity provided by the Internet, changes Not only virtual, but also the real world. All comments are hidden from the index, spam is controlled.