The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula XY(Si,Al)2O6, where X represents calcium (Ca), sodium (Na), iron or magnesium (Mg) and more rarely zinc, manganese or lithium, and Y represents ions of smaller size, such as chromium (Cr), aluminium (Al), magnesium (Mg), cobalt (Co), manganese (Mn), scandium (Sc), titanium (Ti), vanadium (V) or even iron. Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes. They share a common structure consisting of single chains of silica tetrahedra. Pyroxenes that crystallize in the monoclinic system are known as clinopyroxenes and those that crystallize in the orthorhombic system are known as orthopyroxenes.
Melilite refers to a mineral of the melilite group. Minerals of the group are solid solutions of several endmembers, the most important of which are gehlenite and åkermanite. A generalized formula for common melilite is (Ca,Na)2(Al,Mg,Fe2+)[(Al,Si)SiO7]. Discovered in 1793 near Rome, it has a yellowish, greenish-brown color. The name derives from the Greek words meli (μέλι) "honey" and lithos (λίθους) "stone".The name refers to a group of minerals (melilite group) with chemically similar composition, nearly always minerals in åkermanite-gehlenite series.
Chloritoid is a silicate mineral of metamorphic origin. It is an iron magnesium manganese alumino-silicate hydroxide with formula (Fe, Mg, Mn)
2Al
4Si
2O
10(OH)
4. It occurs as greenish grey to black platy micaceous crystals and foliated masses. Its Mohs hardness is 6.5, unusually high for a platy mineral, and it has a specific gravity of 3.52 to 3.57. It typically occurs in phyllites, schists and marbles.
Pigeonite is a mineral in the clinopyroxene subgroup of the pyroxene group. It has a general formula of (Ca,Mg,Fe)(Mg,Fe)Si2O6. The calcium cation fraction can vary from 5% to 25%, with iron and magnesium making up the rest of the cations.
Kutnohorite is a rare calcium manganese carbonate mineral with magnesium and iron that is a member of the dolomite group. It forms a series with dolomite, and with ankerite. The end member formula is CaMn2+(CO3)2, but Mg2+ and Fe2+ commonly substitute for Mn2+, with the manganese content varying from 38% to 84%, so the formula Ca(Mn2+,Mg,Fe2+)(CO3)2 better represents the species. It was named by Professor Bukowsky in 1901 after the type locality of Kutná Hora, Bohemia, in the Czech Republic. It was originally spelt "kutnahorite" but "kutnohorite" is the current IMA-approved spelling.
Apachite is a copper silicate mineral with a general formula of Cu9Si10O29·11H2O. The name is associated with the Apache tribe residents of the area near the Christmas copper mine in the Dripping Spring Mountains of Gila County, Arizona, the location where apachite was first described in 1980.
Marrite (mar'-ite) is a mineral with the chemical formula PbAgAsS3. It is the arsenic equivalent of freieslebenite (PbAgSbS3), but also displays close polyhedral characteristics with sicherite and diaphorite. Marrite was named in honor of geologist John Edward Marr (1857–1933) of Cambridge, England.
Jonesite is a mineral with the chemical formula Ba4(K,Na)2[Ti4Al2Si10O36]*6H2O. This mineral is named after Francis Tucker Jones (1905–1993), who discovered the mineral while working as a Research Chemical Microscopist at Berkeley in CA. Jonesite has diffraction symmetry of mmm, which implies an orthorhombic system with all three axes perpendicular to each other and the angles between each axis equal to 90 degrees. In addition to symmetrical properties, Jonesite is a biaxial mineral with birefringence, which is a term to describe the difference between index of refraction. Jonesite is anisotropic, meaning the speed of light changes through the mineral, so the mineral shows color when viewed in crossed polarized light under a microscope. The mineral also has medium relief, which is a measure of how well the mineral stands out when viewed under a microscope in plane polarized light. In addition to being one of the rarest minerals in the Benitoite Gem mine located in California, Jonesite also is the first titanosilicate mineral with a porous double-layered crystal structure. This discovery is important because titanosilicate frameworks have industrial uses in energy companies and are used in containing radioactive waste.
Kochite is a rare silicate mineral with chemical formula of (Na,Ca)3Ca2(Mn,Ca)ZrTi[(F,O)4(Si2O7)2] or double that. Kochite is a member of the rosenbuschite group.
Amicite is a silicate mineral of the zeolite family. It has a general formula of K2Na2Al4Si4O16·5(H2O). Amicite was described in 1979 from specimens obtained at the Höwenegg quarry in Immendingen, Hegau, in the German state of Baden-Württemberg, which is consequently its type locality. The name is in honor of Giovanni Battista Amici (1786–1863) a botanist, physicist, optician, and inventor of microscope optical elements.
Gabrielite is an extremely rare thallium sulfosalt mineral with a chemical formula of Tl6Ag3Cu6(As,Sb)9S21 or Tl2AgCu2As3S7.
Nambulite is a lithium bearing manganese silicate mineral with the chemical formula (Li,Na)Mn4Si5O14(OH). It is named after the mineralogist, Matsuo Nambu (born 1917) of Tohoko University, Japan, who is known for his research in manganese minerals. The mineral was first discovered in the Funakozawa Mine of northeastern Japan, a metasedimentary manganese ore.
Sewardite is a rare arsenate mineral with formula of CaFe3+2(AsO4)2(OH)2. Sewardite was discovered in 1982 and named for the mineralogist, Terry M. Seward (born 1940), a professor of geochemistry in Zürich, Switzerland.
Eveite is a manganese arsenate mineral in the olivenite group. Its chemical formula is Mn2AsO4OH. It is found only in Långban, Filipstad, Värmland, Sweden and at the Sterling Mine in New Jersey, United States. It is a dimorph of sarkinite and is isostructural with adamite. The name, for the biblical "Eve", comes from its structural similarities to adamite and is also a reference to its apple-green color. It can also be pale yellow. Eveite is an orthorhombic mineral, which means it has three crystallographic axes of unequal lengths which are at 90° to one another.
Kröhnkite ( Na2Cu(SO4)2•2H2O ) is a rare copper sulfate mineral named after B. Kröhnke who first researched it. Kröhnkite may be replaced by Saranchinaite, the anhydrous form of the mineral, if heated to temperatures above 200 °C (392 °F).
Studenitsite is a rare borate mineral with chemical formula of NaCa2[B9O14(OH)4]·2H2O.
Chesterite is a rare silicate mineral that can be compared to amphiboles, micas, and jimthompsonite. Its chemical formula is (Mg,Fe)
17Si
20O
54(OH)
6. Chesterite is named after Chester, Vermont, where it was first described in 1977. The specific geologic setting within its origin is the Carleton talc quarry in Chester, Vermont.
Whiteite is a rare hydrated hydroxyphosphate mineral.
Manganvesuvianite is a rare mineral with formula Ca19Mn3+(Al,Mn3+,Fe3+)10(Mg,Mn2+)2(Si2O7)4(SiO4)10O(OH)9. The mineral is red to nearly black in color. Discovered in South Africa and described in 2002, it was so named for the prevalence of manganese in its composition and its relation to vesuvianite.
Talmessite is a hydrated calcium magnesium arsenate, often with significant amounts of cobalt or nickel. It was named in 1960 for the type locality, the Talmessi mine, Anarak district, Iran. It forms a series with β-Roselite, where cobalt replaces some of the magnesium, and with gaitite, where zinc replaces the magnesium. All these minerals are members of the fairfieldite group. Talmessite is dimorphic with wendwilsonite.
