other names: /
mineral class: depending on the chemical composition
chemical formula: depending on the chemical composition
Chemical elements: depending on the chemical composition
Similar minerals: ?
colour: all colors possible (white, black, red, yellow, green, blue etc.)
shine: Glass gloss
crystal structure: trigonal
mass density: 3,0
magnetism: depending on the chemical composition
Mohs hardness: 7 - 7,5
stroke color: White
transparency: transparent to opaque
General information about tourmaline:
tourmaline describes a mineral which belongs to the ring silicates and which is composed of several chemical elements and compounds. His name comes from the Sinhala language and derives from the word "thuramali" for "colorful stone". Originally, the term tourmaline referred to all gemstones that were imported from Sri Lanka by the Dutch East India Company to Europe. In the Netherlands, due to the pyroelectricity of the stones, which served people in cleaning sea foam pipes, the colloquial name was the Dutch name for "ashes puller".
Tourmalines describe the only group of minerals in which varieties occur in all the colors of the rainbow, as well as from white to black. Colorless specimens are known under the name Achroit, black stones as Schörl. A special feature of the tourmaline group is the multicolour, which lets the stones shine in at least two intense shades, depending on the light and viewing angle. Particularly famous are the so-called watermelon tourmalines, which are colored red and green. Inclusions of gases, other minerals or liquids often cause a cat's eye effect.
Tourmaline forms pyramidal crystals and compact, fine-needle or bulky aggregates. The stroke color is always white, the fracture is musselig. Tourmalines, with a Mohs hardness of up to 7.5, are among the harder minerals, ranging from opaque to completely transparent and of a glassy luster. All representatives of the tourmaline group are insensitive to acids and become electrostatically on heating and subsequent cooling.
Origin and occurrence:
Tourmalines form metamorphic or magmatic and crystallize under the influence of temperatures up to 1100 degrees Celsius as a by-product of a silicate melt. A socialization with feldspar, beryl and quartz is often observed.
In addition to Myanmar and Sri Lanka, deposits are also found in Norway, Greenland, the United States, the United Kingdom, Madagascar and much of Central and Eastern Europe. In addition, tourmalines are also being promoted in Nigeria, Bolivia, Chile, Brazil and Argentina, as well as in India, China and Japan.
Use by humans:
Tourmalines are coveted precious stones thanks to their high Mohs hardness, their low cleavage and their bright colors. Striking multi-colored varieties are also highly sought after by collectors. Intensely turquoise stones are particularly valuable, but even flawless red, green, yellowish green, pink and lilac specimens achieve high prices in the jewelry industry. Because of their pyro- and piezoelectric properties, tourmalines are also used in industrial cleaning of air and water, as a stabilizer and in energy production. From the 19th century, discs made of mineral used in photography as polarizing filters to correct optical impurities such as glossy reflections.