Karlite (kar'-lite) is a silky white to light green

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...

borate mineral The Borate Minerals are minerals which contain a borate anion group. The borate (BO3) units may be polymerised similar to the SiO4 unit of the silicate mineral class. This results in B2O5, B3O6, B2O4 anions as well as more complex structures whic ...

, not to be confused with

tremolite Tremolite is a member of the amphibole group of silicate minerals with composition Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2. Tremolite forms by metamorphism of sediments rich in dolomite and quartz, and occurs in two distinct forms, crystals and fib ...

actinolite Actinolite is an amphibole silicate mineral with the chemical formula . Etymology The name ''actinolite'' is derived from the Greek word ''aktis'' (), meaning "beam" or "ray", because of the mineral's fibrous nature. Mineralogy Actinolite i ...

. It has a general formula of Mg₇(BO₃)₃(OH)₄Cl. Karlite is named in honor of Franz Karl (1918–1972), professor of

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifacts. Specific s ...

and

petrography Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The clas ...

at Christian Albrechts University in

Kiel Kiel ( ; ) is the capital and most populous city in the northern Germany, German state of Schleswig-Holstein. With a population of around 250,000, it is Germany's largest city on the Baltic Sea. It is located on the Kieler Förde inlet of the Ba ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, for his studies of the

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

of the

eastern Alps The Eastern Alps are usually defined as the area east of a line from Lake Constance and the Alpine Rhine valley, up to the Splügen Pass at the Main chain of the Alps, Alpine divide, and down the Liro (Como), Liro River to Lake Como in the south. ...

. Karlite possesses moderate optical relief, the degree to which the mineral grains stand out from the mounting medium. This mineral is orthorhombic and sphenoidal, exhibiting symmetry on 222. Karlite is also enantiomorphic and dihedral. It is a member of the P2₁2₁2₁ space group. This mineral forms optically negative biaxial birefringent crystals, meaning that the 2V angle between the optic axes is bisected by the refractive index direction. Because this mineral possesses birefringence, we know it is anisotropic and will display double refraction; it breaks light into two different rays traveling at different speeds in the mineral. Karlite is a relatively newly discovered borate mineral occurring in clinohumite-

chlorite The chlorite ion, or chlorine dioxide anion, is the halite (oxyanion), halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as s ...

marble Marble is a metamorphic rock consisting of carbonate minerals (most commonly calcite (CaCO3) or Dolomite (mineral), dolomite (CaMg(CO3)2) that have recrystallized under the influence of heat and pressure. It has a crystalline texture, and is ty ...

in calcsilicate-carbonate lenses embedded in

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose ...

. The

amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...

at the original locale is situated between tectonic units "Zentralgneis" and "Schieferhulle". Scholars assume that the high boron concentration needed for the formation of karlite is due to a contact

metasomatism Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is traditionally defined as metamorphism which involves a change in the chemical com ...

created by Hercynian tonalitic

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

s, which make up the "Zentralgneis", although the boron content of karlite is not of commercial importance. This mineral was originally discovered in the Furtschaglkar near the Furtschaglhaus in Austria, but has also been found in Russia and France, and was probably formed during the alpine

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

of the

Alps The Alps () are some of the highest and most extensive mountain ranges in Europe, stretching approximately across eight Alpine countries (from west to east): Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia. ...

.Franz, Gerhard; Ackermand, Dietrich; Koch, Eddie (1981). "Karlite, Mg₇(BO₃₎₃(OH,Cl)₄ a new borate mineral and associated ludwigite from the Eastern Alps." American Mineralogist, 66, 872–877.Bonazzi, P., et al. "Karlite: Crystal Structure and Composition." Neues Jahrbuch für Mineralogie, Monatshefte (1986): 253-262. Print.

References

{{Reflist Borate minerals Magnesium minerals Orthorhombic minerals Minerals in space group 19 Borate chlorides