Analcime or analcite (from the Greek analkimos - "weak") is a white, gray, or colorless tectosilicate mineral. Analcime consists of hydrated sodium aluminium silicate in cubic crystalline form. Its chemical formula is NaAlSi2O6·H2O. Minor amounts of potassium and calcium substitute for sodium. A silver-bearing synthetic variety also exists (Ag-analcite).
Analcime is usually classified as a zeolite mineral, but structurally and chemically it is more similar to the feldspathoids. Analcime occurs as a primary mineral in analcime basalt and other alkaline igneous rocks. It also occurs as cavity and vesicle fillings associated with prehnite, calcite, and zeolites.
|Crystal class||Dipyramidal (mmm) |
H-M symbol: (2/m 2/m 2/m)
|Color||White, colorless, gray, pink, greenish, yellowish|
|Crystal habit||Typically in crystals, usually trapezohedrons, also massive to granular.|
|Twinning||Polysynthetic on , |
|Cleavage||Very poor |
|Fracture||Uneven to subconchoidal|
|Mohs scale hardness||5 - 5.5|
|Specific gravity||2.24 - 2.29|
|Optical properties||Isotropic; anomalously biaxial (-)|
|Refractive index||n = 1.479 - 1.493|
|Other characteristics||Weakly piezoelectric; weakly electrostatic when rubbed or heated.|
Well known locations for sourcing analcime include Croft Quarry in Leicestershire, UK; the Cyclopean Islands east off Sicily and near Trentino in northern Italy; Victoria in Australia; Kerguelen Island in the Indian Ocean; in the Lake Superior copper district of Michigan, Bergen Hill, New Jersey, Golden, Colorado, and at Searles Lake, California in the United States; and at Cape Blomidon, Nova Scotia and Mont Saint-Hilaire, Quebec in Canada; and in Iceland, and now in Namibia.
Blairmorite is a very rare porphyritic volcanic rock characterized by dominant analcime phenocrysts in a matrix of analcime, sanidine and alkalic pyroxene with accessory titanite, melanite and nepheline. It is a leucocratic variety of analcimite (a foidite). Blairmorite has also been described as an analcime-rich variety of phonolite.It was named after the community of Blairmore in southwestern Alberta, Canada.This extrusive igneous rock is known from only two geological formations worldwide. The foremost blairmorite occurrence is the Crowsnest Formation in the Canadian province of Alberta where it is associated with agglomerates and tuffs from explosive eruptions. The other locality is the Lupata Gorge in Mozambique.Boehmite
Boehmite or böhmite is an aluminium oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminium ore bauxite. It is dimorphous with diaspore. It crystallizes in the orthorhombic dipyramidal system and is typically massive in habit. It is white with tints of yellow, green, brown or red due to impurities. It has a vitreous to pearly luster, a Mohs hardness of 3 to 3.5 and a specific gravity of 3.00 to 3.07. It is colorless in thin section, optically biaxial positive with refractive indices of nα = 1.644 - 1.648, nβ = 1.654 - 1.657 and nγ = 1.661 - 1.668.
Boehmite occurs in tropical laterites and bauxites developed on alumino-silicate bedrock. It also occurs as a hydrothermal alteration product of corundum and nepheline. It occurs with kaolinite, gibbsite and diaspore in bauxite deposits; and with nepheline, gibbsite, diaspore, natrolite and analcime in nepheline pegmatites. Industrially, it is used as an inexpensive flame retardant additive for fire-safe polymers.
It was first described by J. de Lapparent in 1927 for an occurrence in the bauxites of Mas Rouge, Les Baux-de-Provence, France, and named for the Bohemian-German chemist Johann Böhm (1895–1952) who carried out X-ray studies of aluminium oxide hydroxides in 1925 (and not for the German geologist Johannes Böhm (1857–1938) as often stated).Callander Bay
Callander Bay is a bay at the extreme east of Lake Nipissing in Parry Sound District, Ontario, Canada. It is approximately four kilometres (2.5 mi) in diameter. The community of Callander is located on its east side.Crowsnest Formation
The Crowsnest Formation, also called the Crowsnest Volcanics, is a geological formation in southwestern Alberta, Canada, on the southwestern margin of the Western Canada Sedimentary Basin. It was named for the Crowsnest Pass near Coleman, Alberta. The formation consists mostly of pyroclastic rocks that were laid down in a series of explosive eruptions about 100 million years ago during the Albian stage of the Early Cretaceous epoch. It contains unusual minerals such as melanite (a variety of andradite garnet) and analcime (a variety of zeolite).Deltoidal icositetrahedron
In geometry, a deltoidal icositetrahedron (also a trapezoidal icositetrahedron, tetragonal icosikaitetrahedron,, tetragonal trisoctahedron and strombic icositetrahedron) is a Catalan solid. Its dual polyhedron is the rhombicuboctahedron.Donnayite-(Y)
Donnayite-(Y) is a rare-earth carbonate mineral containing the rare-earth metal yttrium. It was first discovered in 1978 at Mont Saint-Hilaire, Quebec. Donnayite was subsequently identified and named after Joseph D. H. Donnay and his wife, Gabrielle Donnay. Both were prominent mineralogists and crystallographers, and J. D. H. Donnay was awarded the Roebling Award by the Mineralogical Society of America in 1971 for his emphasis on the importance of optical mineralogy and crystal morphology. Donnayite tends to occur in small quantities in the pegmatite dykes and miarolitic cavities of mountainous regions. It crystallizes in this environment with increasing alkalinity values until the alkalinity suddenly drops during the last stage of crystallization. This results in increasing amounts of Na carbonates and REE minerals. First discovered at Mont St-Hilaire, donnayite has since been found in the Southern Ural Mountains of Russia and the Narssarssuk pegmatite of South Greenland. Donnayite crystals tend to be small and the color is commonly pale yellow to yellow with a white streak and a vitreous luster. Donnayite crystals usually display trigonal or hexagonal symmetry and have a hardness of 3. Twinning is extremely common in this mineral. Minerals closely related to donnayite include synchysite, calcite, sphalerite, microcline, and analcime. Donnayite is isomorphous with weloganite and mckelveyite.Edingtonite
Edingtonite is a white, gray, brown, colorless, pink or yellow zeolite mineral. Its chemical formula is BaAl2Si3O10·4H2O. It has varieties with tetragonal, orthorhombic or triclinic crystals.The mineral occurs within cavities in nepheline syenites, carbonatites, in
hydrothermal veins and various mafic rocks. It occurs associated with thomsonite, analcime, natrolite, harmotome, brewsterite, prehnite and calcite.The mineral was first reported by and named for Scottish mineral collector James Edington (1787–1844). Other sources (including the mineralogist Haidinger) credit Scottish geologist and mineralogist Thomas Edington (1814-1859). However, as the mineral was named in 1825, the former accreditation must be the true one.Feldspathoid
The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rocks, and are not found in rocks containing primary quartz.Foid, contraction of the term feldspathoid, is applied to any igneous rock containing up to 60% modal feldspathoid minerals. For example, a syenite with significant nepheline present can be termed a '(nepheline)-bearing syenite', or a '(nepheline)-syenite', with the term (nepheline) replaceable by any 'foid' mineral. Such terminology is used in the Streckeisen (QAPF) classification of igneous rocks.Gai-As Formation
The Gai-As Formation is an Early to Middle Permian (Kungurian to Wordian) geologic formation correlated with the Ecca Group and designated "Ecca" Group, because it does not belong to the Karoo, in the southwestern Kunene Region and northern Erongo Region of northwestern Namibia. The Gai-As Formation represents the second-oldest sedimentary unit of the Huab Basin, overlying the Huab Formation. The formation was deposited in a fluvial to lacustrine setting.
The Gai-As Formation is correlated with a series of formations in the Pelotas and Paraná Basins in southeastern Brazil, deposited in a larger basinal area, 150 million years before the break-up of Pangea. The abundance of Glossopteris and Mesosaurus fossils in the underlying Huab Formation are characteristic of the Gondwanan correlation across present-day South America, Africa, Antarctica and Australia. The Gai-As Formation has provided fossil bivalves and an indeterminate stereospondylid.Highwood Mountains
The Highwood Mountains are an island range (sub-range of the Rockies entirely surrounded by prairie) which cover approximately 4,659 km² (1,799 sq mi) of north central Montana in the U.S.. They are in Chouteau, Judith Basin and Cascade counties and lie east of Great Falls and Benton Lake National Wildlife Refuge, at the northern end of the Lewis and Clark National Forest. The mountains were included in Highwood Mountains National Forest until 1908, when the unit became part of Lewis and Clark National Forest.
Nearby are Highwood, Montana and the Missouri River above the mouth of the Marias River. The highest point in the Highwood Mountains is Highwood Baldy at 2338 meters (7670 ft).The area has volcanic origins and is rich in potash. Many of the extrusive rocks and some of the dike rocks contain abundant phenocrysts of a clear analcime that appears to be primary. Pseudoleucite is an abundant constituent of many of the igneous rocks. The Shonkin Sag, a glacial meltwater channel, borders the Highwood Mountains to the north.Pentagonite
Pentagonite is a rare silicate mineral with formula Ca(VO)Si4O10·4(H2O).
It was named for the unusual twinning which produces an apparent five-fold symmetry. It is a dimorph of cavansite.
Pentagonite was first described in 1973 for an occurrence in Lake Owyhee State Park, Malheur County, Oregon. It has also been reported from the Pune district of India. It occurs as fracture and cavity fillings in tuff and basalt. It occurs with cavansite, heulandite, stilbite, analcime, apophyllite and calcite.Pollucite
Pollucite is a zeolite mineral with the formula (Cs,Na)2Al2Si4O12·2H2O with iron, calcium, rubidium and potassium as common substituting elements. It is important as a significant ore of caesium and sometimes rubidium. It forms a solid solution series with analcime. It crystallizes in the isometric - hexoctahedral crystal system as colorless, white, gray, or rarely pink and blue masses. Well formed crystals are rare. It has a Mohs hardness of 6.5 and a specific gravity of 2.9. It has a brittle fracture and no cleavage.Sabinaite
Sabinaite (Na4Zr2TiO4(CO3)4) is a rare carbonate mineral. It crystallizes in the monoclinic crystal system as colorless to white prisms within cavities. It is more typically found as powdery coatings and masses. It has a specific gravity of 3.36.
It has been found in vugs in a carbonatite sill on Montreal Island and within sodalite syenite in the alkali intrusion at Mont Saint-Hilaire in Quebec, Canada.
It was first described in 1980 for an occurrence in the Francon quarry, Montreal Island. It is named after Ann Sabina (1930–2015), a mineralogist working for the Geological Survey of Canada.Scawtite
Scawtite is a hydrous calcium silicate mineral with carbonate, formula: Ca7(Si3O9)2CO3·2H2O. It crystallizes in the monoclinic crystal system as thin plates or flat prisms.Scawtite was first described in 1929 for an occurrence at Scawt Hill in Northern Ireland.Scawtite occurs as in skarns and hydrothermal veins in limestone. Associated minerals include melilite, spurrite, tobermorite, thomsonite, larnite, grossular, bultfonteinite, calcite, analcime, foshagite and hillebrandite.Thaumasite
Thaumasite is a silicate mineral with chemical formula Ca3Si(OH)6(CO3)(SO4)·12H2O. It occurs as colorless to white prismatic hexagonal crystals, typically as acicular radiating groups. It also occurs as fibrous masses. Its Mohs hardness is 3.5 and it has a specific gravity of 1.88 to 1.90. Optically it is uniaxial negative with indices of refraction of nω = 1.507 and nε = 1.468.
It occurs as a hydrothermal alteration mineral in sulfide ore deposits and geothermal alteration of basalt and tuff. It occurs with zeolites, apophyllite, analcime, calcite, gypsum and pyrite.Thaumasite can also be formed along with other calcium silicate hydrates (CSH) during cement alteration, especially when sulfate attack develops.
It was first described in 1878 in Sweden and named from the Greek, "thaumazein", to be surprised, in reference to its unusual composition with carbonate, sulfate and hydroxysilicate anions.The silicate structure of thaumasite is unusual due to the presence of non-tetrahedral silicon in its crystal lattice. Indeed, an atypic octahedral configuration is observed for Si present in thaumasite in the form of hexahydroxysilicate: [Si(OH)6]2−, a species exhibiting a geometry similar to that of the hexafluorosilicate [SiF6]2−.Theralite
Theralite (from Greek "to pursue") is, in petrology, the name given to calcic foidal gabbro, a plutonic hylocrystalline rock consisting of augite, olivine, calcic plagioclase (labradorite), and nepheline, along with accessories including biotite, magnetite, ilmenite and analcime.
Theralite is the intrusive equivalent of nepheline basanite, a foidal basalt with essential calic plagioclase and essential olivine. Tephrite is foidal basalt with essential calic plagioclase but without essential olivine. It is essentially the volcanic equivalent of essexite. The discovery of theralite was looked forward to with interest as completing the series of basic rocks containing nepheline as an essential constituent.
With the increase in silica (SiO2) and the concomitant reduction in nepheline, theralite becomes gabbro. With a decrease in silica and reduction in olivine theralite grades into teschenite and with the addition of sodic feldspar, grades into essexite. With a further reduction in silica such that there is no feldspar these rocks become melteigites. With the addition of alkali feldspar replacing or becoming more dominant than calcic plagioclase theralites grade into foidal syenite, including shonkinite.
Properly theralite is only for a specific type of calcic foidal gabbro, those with essential nepheline and without essential analcime or sodic feldspar.Trachybasalt
Trachybasalt is a volcanic rock with a composition between trachyte and basalt. Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and likely very small amounts of leucite or analcime. Trachybasalt is a basalt with high alkali content (5 to 7% Na2O + K2O, see TAS diagram).Wairakite
Wairakite is a zeolite mineral with an analcime structure but containing a calcium ion. The chemical composition is Ca8(Al16Si32O96)•16H2O. It is named for the location of its discovery in Wairakei, North Island, New Zealand, by Alfred Steiner in 1955. The first finds were in hydrothermally altered rhyolitic tuffs, ignimbrites and volcaniclastic rocks. The mineral has since been found in metamorphic rocks and in geothermal areas. It was most likely first successfully synthesized in a laboratory in 1970.Zeolite
Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts. The term zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that rapidly heating the material, believed to have been stilbite, produced large amounts of steam from water that had been adsorbed by the material. Based on this, he called the material zeolite, from the Greek ζέω (zéō), meaning "to boil" and λίθος (líthos), meaning "stone". The classic reference for the field has been Breck's book Zeolite Molecular Sieves: Structure, Chemistry, And Use.Zeolites occur naturally but are also produced industrially on a large scale. As of December 2018, 245 unique zeolite frameworks have been identified, and over 40 naturally occurring zeolite frameworks are known. Every new zeolite structure that is obtained is examined by the International Zeolite Association Structure Commission and receives a three letter designation.