CERUSSITE
CERUSSITE Cerussite – PbCO3 – is a carbonate with a more restricted distribution, generally associated with Pb ores. As it contains 77.5% Pb, it can constitute an important ore. It is classified in the Aragonite Group and is usually very pure, but may contain Ag and Cr. It forms a series with strontianite (from Sr). […]
CELADONITE
CELADONITE Celadonite is a phyllosilicate from the Mica Group. It is a very common clay mineral in volcanic rocks. It has no economic importance. For decades it was believed that celadonite and glauconite were the same mineral. In addition, celadonite was often confused with malachite because the colors, macroscopically, are indeed quite similar. Celadonite can […]
CATAPLEIITE
CATAPLEIITE Catapleiite – Na2Zr(Si3O9)·2H2O – is a very rare cyclosilicate, occurring in alkaline plutonic rocks. It is not important as an ore, but crystals fetch very high prices in the collector’s mineral market, on the order of several thousand dollars per piece. It is classified in the Catapleiite Group, being the monoclinic dimorph of gaidonnayite. […]
CLINOHUMITE
CLINOHUMITE Clinohumite – Mg9(SiO4)4(OH,F)2 – is a very rare nesosilicate. It does not constitute ore. It is the monoclinic member of the Humite Group and may contain Ca, Mn, Fe, Ti and (OH) as impurities. Clinohumite forms an isomorphic series with hydroxyclinohumite (defined only in 1998, so care is needed with older literature). It is […]
CORDIERITE
CORDIERITE Cordierite – (Mg,Fe)2Al4Si5O18 – is a rarer cyclosilicate, a mineral typical of contact metamorphic rocks. Synthetic cordierite is used in the manufacture of catalytic converters. Natural cordierite is only economically important when violet and transparent: in this case it is called “iolite” and used as a gemstone. It forms a series with sekaninaite, an […]
CHLORITOID
CHLORITOID Chloritoid – (Fe2+,Mg,Mn)2(Al,Fe3+)Al3O2(SiO4)2(OH)4 – is a relatively rare nesosilicate, characteristic of some specific types of metamorphic rocks. It has no economic importance. The mineral is part of the Chloritoid Group and forms a series with carboirite, an extremely rare triclinic nesosilicate that occurs in only one location in the world (France). “Sismondine” is a […]
CANCRINITE
CANCRINITE Cancrinite – (Na,Ca,K)6-8(AlSiO4)(CO3,SO4,Cl)1-2.n1-5H2O – is a tectosilicate of the Feldspathoid Group. It is a rare mineral, from alkaline igneous rocks such as syenites. It has no economic importance. Cancrinite forms a solid solution with vishnevite, forming a series. May contain Fe, Ti, Mg, K, Cl and S. Yellow cancrinite may fluoresce in intense citric […]
CINNABAR
CINNABAR Cinnabar – HgS – is a relatively common sulfide and is the most common ore of mercury. It is trimorph with metacinnabar and hypercinnabar. One variety is “hepatic cinnabar”, a mixture of cinnabar with bituminous and earthy matter that occurs in the mines of Idrija, Slovenia. When hepatic cinnabar appears in curved lamellar crystals, […]
CRISTOBALITE
CRISTOBALITE Cristobalite – SiO2 – is a very rare tectosilicate that occurs mainly associated with intermediate and acidic volcanic rocks. It has no economic importance. It is one of the polymorphs of SiO2, with quartz, β-quartz, tridymite, coesite and stishovite. Cristobalite is high temperature and low pressure. It is metastable at room temperature: there is […]
CHALCOPYRITE
CHALCOPYRITE Chalcopyrite – CuFeS2 – is a very common sulfide, found in many types of rocks and ores. It is the most common and abundant copper ore, containing 25% Cu by weight. It forms a series with eskebornite (CuFeSe2). On the rare occasions that it forms idiomorphic crystals, it shows striations parallel to (1-10) on […]