Quintinite
Encyclopedia
Quintinite is a carbonate mineral with the chemical formula Mg4Al2(OH)12CO3⋅H2O.
The mineral was named after Quinitin Wight of Ottawa, Ontario, Canada (b. 1935), who was a significant contributor to mineral studies at Mont Saint-Hilaire
.
Quintinite is found as 2H and 3T, or 2-hexagonal and 3-trigonal, polytypes, which were originally approved as separate species, but have not been considered species since 1998. These hexagonal and trigonal forms of quinitinite are both from the hexagonal crystal systems, meaning they both have similar lengths of their crystal axes and the same angles between these axes. As a hexagonal mineral, quintinite has three axes of equal length at 60 degree angles to one another and a c axis perpendicular to these three axes of a different length. 2H occurs in carbonatite
at Jacupiranga
, São Paulo
, Brazil
, in the Jacupiranga mine and 3T occurs with minerals like gonnardite
and donnayite. Both polytypes occur in hydrothermal vent
s in alkaline rocks. Herg (1977) interpreted the Jacupiranga area as related to a hotspot
. The 3T polytype was originally found in the Poudrette quarry at Mont Saint-Hilaire
, which is a rare alkaline intrusive complex. The 2H polytype is pleochroic, meaning that the mineral changes colors (in this case yellow and light yellow) when viewed at different angles under a polarizing petrographic microscope. The 3T polytype, however, is not commonly pleochroic but can show green pleochroism if it is high in iron. The 3T polytype has a positive index of refraction whereas the 2H polytype can possess crystals with either a positive or a negative index of refraction.
The mineral was named after Quinitin Wight of Ottawa, Ontario, Canada (b. 1935), who was a significant contributor to mineral studies at Mont Saint-Hilaire
Mont Saint-Hilaire
Mont Saint-Hilaire , is an isolated hill, high, in the Montérégie region of southern Quebec. It is about thirty kilometres east of Montreal, and immediately east of the Richelieu River. It is one of the Monteregian Hills...
.
Quintinite is found as 2H and 3T, or 2-hexagonal and 3-trigonal, polytypes, which were originally approved as separate species, but have not been considered species since 1998. These hexagonal and trigonal forms of quinitinite are both from the hexagonal crystal systems, meaning they both have similar lengths of their crystal axes and the same angles between these axes. As a hexagonal mineral, quintinite has three axes of equal length at 60 degree angles to one another and a c axis perpendicular to these three axes of a different length. 2H occurs in carbonatite
Carbonatite
Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....
at Jacupiranga
Jacupiranga
Jacupiranga is a municipality in the state of São Paulo in Brazil. The population in 2004 is 18,380 and the area is 709.98 km². The elevation is 33 m. This place name comes from the Tupi language.-External links:**...
, São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, in the Jacupiranga mine and 3T occurs with minerals like gonnardite
Gonnardite
Gonnardite is a comparatively rare, fibrous zeolite, natrolite subgroup. Older papers claim that a complete solid solution exists between tetranatrolite and gonnardite, but tetranatrolite was discredited as a separate species in 1999...
and donnayite. Both polytypes occur in hydrothermal vent
Hydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
s in alkaline rocks. Herg (1977) interpreted the Jacupiranga area as related to a hotspot
Hotspot
Hot spot generally refers to small areas of intense or important activity embedded in a larger area of relative calm. Specifically, it may refer to:-Arts and entertainment:* Hot Spot , a 1963 Musical...
. The 3T polytype was originally found in the Poudrette quarry at Mont Saint-Hilaire
Mont Saint-Hilaire
Mont Saint-Hilaire , is an isolated hill, high, in the Montérégie region of southern Quebec. It is about thirty kilometres east of Montreal, and immediately east of the Richelieu River. It is one of the Monteregian Hills...
, which is a rare alkaline intrusive complex. The 2H polytype is pleochroic, meaning that the mineral changes colors (in this case yellow and light yellow) when viewed at different angles under a polarizing petrographic microscope. The 3T polytype, however, is not commonly pleochroic but can show green pleochroism if it is high in iron. The 3T polytype has a positive index of refraction whereas the 2H polytype can possess crystals with either a positive or a negative index of refraction.