Tabla de Contenidos
Below is a list of the best known black minerals and their particularities:
- tourmaline
- Magnetite
- hematite
- Quartz
- chromite
- Augite
- Biotite
- hornblende
- ilmenite
- rutile
- stilpnomelana
- pyrolusite
- neptunite
Characteristics of black minerals
tourmaline
Tourmaline’s name comes from the Sinhala term touramalli , which means “stone of mixed colours”. In nature there are eleven colors of tourmaline. Colored tourmaline is considered a gemstone.
Black tourmaline can be found in high-grade pegmatites, granites, and some schists. It usually forms prismatic crystals. Unlike augite or hornblende, tourmaline has a hardness of 7 to 7.5 on the Mohs scale. It also has a vitreous luster and can be transparent or translucent.
Black tourmaline is used for the manufacture of pressure measuring instruments and as an amulet. It is given properties for emotional stabilization, protection and healing.
Magnetite
Magnetite, also known as lodestone because it attracts amounts of iron, is a common mineral in coarse-grained igneous rocks and metamorphic rocks. It may be grayish-black in color or have a rusty coating. The crystals are common, with fluted faces in the form of octahedrons or dodecahedrons.
Magnetite has a metallic luster and a hardness of 6 on the Mohs scale. It is used in pigments, as an indicator of hydrothermal alterations, as a micronutrient in fertilizers and in the manufacture of other chemical products. In meditation it is used to strengthen the pineal gland and intuition. Furthermore, it is said to have the property of influencing a person’s bioenergetic field.
hematite
Hematite is a black or brownish-black oxide of iron. It is most common in low-grade sedimentary and metasedimentary rocks. It varies greatly in shape and appearance, but is usually streaked with reddish hues. Its luster can be dull to semi-metallic and it has a hardness of 5.5 to 6.5 on the Mohs scale.
Hematite is used for the manufacture of pigments and polishing powders. It is also used for the separation of heavy metals or as radiation protection. Healing properties are attributed to it, especially related to self-love, concentration and energy.
Another particularity of this mineral is that, according to NASA, it is found in abundant quantities on the planet Mars.
Quartz
Black quartz is a prismatic mineral that is black, dark brown, or dark gray in color. It is translucent, has a vitreous luster and a hardness of 7 on the Mohs scale. It is quite common to find it in nature.
Black quartz is used to make jewelry and is of great importance in esotericism. It is associated with tranquility, happiness, good fortune, and personal growth.
chromite
Chromite is an oxide of chromium-iron found in peridotite and serpentinite. It can also appear in thin layers in large plutonic rocks or ancient magma bodies. Sometimes it is found in meteorites. It is similar to magnetite, but it rarely forms crystals and has almost no magnetic properties.
Its characteristics include its grayish or brownish black color, its metallic luster and its hardness of 5.5 on the Mohs scale.
Chromite is used as a refractory material and is highly prized in industry, especially in the production of stainless steel.
other black minerals
Augite
Augite is a standard black or brown-black pyroxene mineral found in dark igneous rocks and some high-grade metamorphic rocks. Its name comes from the Greek term auge , which means shine. It is also known as violatite.
Its crystals are rectangular in cross section and give it a particular vitreous luster. It has a hardness of 5 to 6 on the Mohs scale.
The augite is not usually exploited in mining, since it does not have an economic value. However, some rare specimens of augite are highly prized by mineral collectors.
Biotite
This mineral belongs to the group of micas. It forms shiny, flexible flakes that are deep black or brownish-black in color. Biotite crystals are found in pegmatites and are abundant in other igneous and metamorphic rocks. Its vitreous to pearly luster and its hardness of 2.5 to 3 on the Mohs scale stand out.
Biotite is used as an electrical or thermal insulator, as an indicator of potassium alteration, paint filler and other products.
hornblende
Hornblende is a mineral that can be found in igneous and metamorphic rocks. Its crystals are shiny black, dark brown, or dark green, and can be short or long, and even needle-shaped in amphibolite schists. It has a vitreous luster and a hardness of 5 to 6 on the Mohs scale.
Hornblende is used for road construction and the manufacture of black granite, which, in turn, is used in building cladding and floor tiles.
ilmenite
Crystals of this titanium oxide mineral can be found in many igneous and metamorphic rocks, but it occurs in greatest quantity in pegmatites. Ilmenite is barely magnetic. Its color can vary from dark brown to red.
It has a submetallic luster and a hardness of 5 to 6 on the Mohs scale.
rutile
Rutile is a titanium oxide mineral that generally forms long, ridged prisms or flat plates. Its crystals are found in coarse-grained igneous and metamorphic rocks. It is also known by the names paraedrite, crispite, and edisonite.
Rutile has a dark reddish color, metallic luster to adamantine, and a hardness of 6 to 6.5 Mohs. It is mainly used as a pigment.
stilpnomelana
This glowing black mineral is rare. It is related to micas and is found mainly in high-pressure metamorphic rocks with high iron content. Unlike biotite, its scales are more brittle than flexible. It has a vitreous to pearly luster and has a hardness of 3 to 4 on the Mohs scale.
Pyrolusite / Manganite / Psilomelan
They are manganese oxide minerals that usually form large veins. The mineral-forming black dendrites between sandstone beds are generally pyrolusite; the crusts are generally called psilomelan. Its characteristics include its dark gray to black color, sometimes bluish, its metallic to opaque luster and its hardness from 2 to 6.5 on the Mohs scale.
Pyrolusite is used as a component of steel, batteries, chlorine, and in the manufacture of dyes. It is also appreciated as an ornamental stone.
neptunite
Neptunite is one of the rarest black minerals. Its crystals are prismatic. It is found in veins of natrolite and is usually black to dark reddish-brown in color. It has a hardness of 5 to 6 on the Mohs scale.
Bibliography
- Maldonado, Y. (May 20, 2020). Black Minerals: Names and Listing . Geologyweb. https://geologiaweb.com/minerales/minerales-negros/
- Bonewitz, RL Rocks and minerals. Definitive Visual Guide . (2008). Spain. Omega.
