One of the most common rock-forming minerals is hornblende. This is the common name for amphiboles, formed from two German words - "horn" and "dazzle". When split, the crystals of this mineral look like a horn.
External description and properties
The appearance of hornblende makes it easy to identify it among other minerals. It is distinguished by intergrown short-columnar crystals with a hexagonal or rhombic cross section.
This is a fairly hard opaque mineral with a low specific gravity and unique cleavage. The hardness index is 5.5-6 on the mineralogical scale. The density of hornblende is on average from 3100 to 3300 kg/m³. Cleavage is marked in two directions at an angle of 124 degrees.
Hornblende does not vary in color. It can be from light green to brownish-black (usually these are bas altic rocks with a high content of alkaline compounds). Minerals of any color have an equally beautiful glassy, semi-metallic luster with overflows. This breed is not exposedthe effect of acids. May melt into dark green glass if heated strongly.
Chemical composition
He is fickle and varies quite widely. The ratios of aluminum to ferric iron, as well as magnesium to ferrous, change. Perhaps the predominance of potassium over magnesium.
In the presence of a high content of titanium (up to 3%), the mineral is called "bas altic hornblende". The composition is generated depending on the totality of chemical elements, among which potassium oxide can be from 10 to 13%, ferrous oxide - from 9.5 to 11.5%, iron oxide - 3-9%, magnesium oxide - 11-14%, sodium oxide - 1.5%, silicon dioxide - 42-48%, aluminum oxide - 6-13%.
During weathering, the rock decomposes into opals and carbonates. Interaction with hydrothermal solutions leads to the transformation of the mineral into chlorite, epidote, calcite and quartz.
Under the influence of various physical factors, the rock can undergo complex chemical processes leading to the formation of intermediate compositions.
Origin
Hornblende is a rock-forming mineral and the main component of amphibolites, shales and gneisses. It occurs, as a rule, during the impact of pegmatites on igneous rocks. It is sometimes found in volcanic ash as single crystals. In the form of primary material in rocks that have flowed to the surface, this mineral is quite rare.
Common hornblende described above can transform into bas alt. This usually happens in lava flows, under oxidizing conditions and heating to a temperature of 800 ⁰С. This process is easy enough to create artificially.
Deposits
Large hornblende crystals are rare and therefore of great interest to collectors. They are observed mainly in gabbro pegmatites, which are not so numerous. In the Urals, in the region of Mount Sokolina, well-formed crystals up to 0.5 m long were found. Very beautiful specimens of this mineral are found in the Czech Republic, Norway, and also in the volcanic lava of Vesuvius in Italy.
Hornblende is widespread in the German Ore Mountains, rich in lime-silicate rock. The Meissen syenite massif is known for its rich deposits of this mineral. Large deposits of crystals are located in Burma.
Scope of application
The main application of this mineral found in industry. Under certain technological processes, hornblende has the ability to transform into calcite, epidote, quartz, chlorite, and form carbonates and opals during decomposition. It is used as a raw material for the manufacture of dark green glass, as well as in construction as part of granite.
Fragility and lack of visual appeal do not allow the use of this mineral in jewelry. But the inclusion of hornblende in quartz products allows you to create a beautiful stone, the brilliance and shape of which can beadmire.
There is hornblende in the composition of the mineral called "Apache tears", which is a type of obsidian. It is believed that this stone has the ability to help a person cope with various misfortunes, attracts good luck.
Specialists studying lithotherapy talk about the positive effect of the mineral on the immune system, digestive and excretory. It is enough just to wear jewelry from it - beads, pendants, etc.
