| Formula |
|(Na, Ce)(Y, REE)(HCO3)(OH)3·4(H2O)|
|Crystal class|| Sphenoidal (2) |
(same H-M symbol)
|Formula mass||375.77 g/mol|
|Crystal habit||Blocky crystals, pseudo-tetragonal|
|Twinning||Common on (101)|
|Cleavage|| perfect,  parting|
|Mohs scale hardness||2–3|
|Diaphaneity||Translucent to transparent|
|Optical properties||pseudouniaxial negative 2V (meas.) ≤ 5°|
|Refractive index||nα = 1.40, nβ = 1.540, nγ = 1.540|
|Birefringence||δ = 0.140|
|Other characteristics||Radioactivity 770 Bq/g|
Thomasclarkite-(Y) is a rare mineral which was known as UK-93 until 1997, when it was renamed in honour of Thomas H. Clark (1893–1996), McGill University professor. The mineral is one of many rare-earth element minerals from Mont Saint-Hilaire. The only reported occurrence is in an alkalic pegmatite dike in an intrusive gabbro-nepheline syenite.
Thomas Henry Clark, Ph.D., FRSC was a Canadian geologist who is considered to have been one of the nation's top scientists of the 20th century. He was a professor who authored over 100 scientific publications. After his death, a mineral was named in his honour.
McGill University is a public research university in Montreal, Quebec, Canada. It was established in 1821 by royal charter, granted by King George IV. The university bears the name of James McGill, a Montreal merchant originally from Scotland whose bequest in 1813 formed the university's precursor, McGill College.
A mineral is, broadly speaking, a solid chemical compound that occurs naturally in pure form. A rock may consist of a single mineral, or may be an aggregate of two or more different minerals, spacially segregated into distinct phases. Compounds that occur only in living beings are usually excluded, but some minerals are often biogenic and/or are organic compounds in the sense of chemistry. Moreover, living beings often syntesize inorganic minerals that also occur in rocks.
Kogarkoite is a sodium sulfate fluoride mineral with formula Na3(SO4)F. It has a pale blue color, a specific gravity of about 2.67 and a hardness of 3.5. The crystal is monoclinic and is a type of naturally occurring antiperovskite. Kogarkoite is named after the Russian petrologist Lia Nikolaevna Kogarko (born 1936) who discovered the mineral.
Astrophyllite is a very rare, brown to golden-yellow hydrous potassium iron titanium silicate mineral. Belonging to the astrophyllite group, astrophyllite may be classed either as an inosilicate, phyllosilicate, or an intermediate between the two. It forms an isomorphous series with kupletskite, to which it is visually identical and often intimately associated. Astrophyllite is of interest primarily to scientists and collectors.
Arfvedsonite is a sodium amphibole mineral with composition: [Na][Na2][(Fe2+)4Fe3+][(OH)2|Si8O22]. It crystallizes in the monoclinic prismatic crystal system and typically occurs as greenish black to bluish grey fibrous to radiating or stellate prisms.
Halotrichite, also known as feather alum, is a highly hydrated sulfate of aluminium and iron. Its chemical formula is FeAl2(SO4)4·22H2O. It forms fibrous monoclinic crystals. The crystals are water-soluble.
Aegirine is a member of the clinopyroxene group of inosilicates. Aegirine is the sodium endmember of the aegirine-augite series. Aegirine has the chemical formula NaFeSi2O6 in which the iron is present as Fe3+. In the aegirine-augite series the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance the charge. Aluminium also substitutes for the iron(III). It is also known as acmite, which is a fibrous, green-colored variety.
Abenakiite-(Ce) (IMA1991-054) is a mineral of sodium, cerium, neodymium, lanthanum, praseodymium, thorium, samarium, oxygen, sulfur, carbon, phosphorus, and silicon with a chemical formula Na26Ce6(SiO3)6(PO4)6(CO3)6(S4+O2)O. The silicate groups may be given as the cyclic Si6O18 grouping. The mineral is named after the Abenaki, an Algonquian Indian tribe of New England. Its Mohs scale rating is 4 to 5.
Nenadkevichite is a rare silicate mineral containing niobium with formula: (Na,Ca)(Nb,Ti)Si2O7·2H2O. It forms brown to yellow to rose colored orthorhombic dipyramidal crystals with a dull to earthy luster. It has a Mohs hardness of 5 and a specific gravity of 2.86.
Kukharenkoite-(Ce) is a barium cerium fluoride carbonate mineral, formula Ba2CeF(CO3)3. It was identified from samples found in the Mont-Saint-Hilaire alkaline intrusive complex, Quebec, and the Khibiny Massif, Kola peninsula, Russia. It was named for Russian mineralogist Alexander A. Kukharenko (1914–1993).
Mckelveyite-(Y) is a hydrated sodium, barium, yttrium, and uranium–containing carbonate mineral, with the chemical formula Ba3Na(Ca,U)Y(CO3)6·3H2O.
Normandite is a brittle orange brown sorosilicate mineral discovered in 1997 by Charles Normand, of Montreal. Normandite occurs in Khibiny Massif, Kola, Russia; in Poudrette quarry, Mont-Saint-Hilaire, Quebec and Tenerife, Canary Islands. It is found in nepheline syenite and in miarolitic cavities in nepheline syenite, associated with nepheline, albite, microcline, aegirine, natrolite, catapleiite, kupletskite, eudialyte, cancrinite, villiaumite, rinkite, and donnayite-(Y).
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.
Siderophyllite is a rare member of the mica group of silicate minerals with formula KFe2+2Al(Al2Si2)O10(F,OH)2.
Carletonite is a rare silicate mineral with formula KNa4Ca4(CO3)4Si8O18(F,OH)·(H2O).
Stillwellite-(Ce) is a rare-earth boro-silicate mineral with formula: (Ce,La,Ca)BSiO5.
Quintinite is a carbonate mineral with the chemical formula Mg4Al2(OH)12CO3⋅3H2O.
Narsarsukite is a rare silicate mineral with chemical formula Na2(Ti,Fe3+)Si4(O,F)11 or Na4(Ti,Fe)4[Si8O20](O,OH,F)4.
Poudretteite is an extremely rare mineral and gemstone that was first discovered as minute crystals in Mont St. Hilaire, Quebec, Canada, during the 1960s. The mineral was named for the Poudrette family because they operated a quarry in the Mont St. Hilaire area where poudretteite was originally found.
Khomyakovite is an exceedingly rare mineral of the eudialyte group, with formula Na12Sr3Ca6Fe3Zr3WSi(Si9O27)2(Si3O9)2O(O,OH,H2O)3(OH,Cl)2. The original formula was extended to show the presence of both the cyclic silicate groups and M4-site silicon, according to the nomenclature of the eudialyte group. Some niobium substitutes for tungsten in khomyakovite. Khomyakovite is an iron-analogue of manganokhomyakovite, the second mineral being a bit more common. The two minerals are the only group representatives, beside taseqite, with species-defining strontium, although many other members display strontium diadochy. Khomyakovite is the third eudialyte-group mineral with essential tungsten (after johnsenite-(Ce) and manganokhomyakovite).
Manganokhomyakovite is a very rare mineral of the eudialyte group, with formula Na12Sr3Ca6Mn3Zr3WSi(Si9O27)2(Si3O9)2O(O,OH,H2O)3(OH,Cl)2. This formula is in extended form (based on the original one), to show the presence of cyclic silicate groups and domination of silicon at the M4 site, basing on the nomenclature of the eudialyte group. Some niobium substitutes for tungsten in khomyakovite. As suggested by its name, manganokhomyakovite is a manganese-analogue of khomyakovite, the latter being more rare. The two minerals are the only group representatives, beside taseqite, with species-defining strontium, although many other members display strontium diadochy. Manganokhomyakovite is the third eudialyte-group mineral with essential tungsten (after johnsenite-(Ce) and khomyakovite).
Charleshatchettite is a very rare, complex, niobium oxide mineral with the formula CaNb4O10(OH)2•8H2O. It was discovered in the mineral-rich site Mont Saint-Hilaire, Montérégie, Québec, Canada.
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