CompuServe Messages

Hi, Bill– There follows a copy of an earlier message in which I reported a talk on Greenland minerals, followed by a report from my locales database (part of ROCKDB.ARC in this forum's library) for Greenland fluorescents. Being mainly from Robbin's earlier book, it is dominated by fluorescent minerals not known in the U.S.; looking at lists from a Mineralogical Record issue devoted to Greenland (Mar. 93), I rather expect there are many other fluorescents which Manny excluded because of matches in the U.S. The tugtupite locale is exhausted, I have since heard; this is a pity since it is the prize fluorescent mineral from Greenland, also exhibiting a reversible color change as noted below. In its visible-light pink state, it makes a fine lapidary material. –Doug #107904 S12/Geology 23-Sep-93 20:08:50 Sb: Greenland minerals Fm: Doug Mitchell 70621,702 To: all Hi, folks– Dr. Ole Petersen of the Copenhagen University gave a talk on Greenland minerals at the Denver show. Many of the minerals mentioned were in his exhibit on the main floor. There are 300+ minerals known in Greenland, which is 2700 km long, and 700 km south of the north pole. The ice free zones are narrow bands at the coasts; the west coast ice free zone is 250 km wide, characterized by glacier erosion. Narsarsuk is one of two air arrival points on west coast (at a former US Air Force base); from there travel is by helicopter, boat, or walking. The southern margins of Greenland are mainly crystalline rocks of the precambrian shield, multiply metamorphosed. Nuuk is the type locale of sapphirine and kornerupine(?) discovered by Steenstrup. Sapphirines are found in 40 locales, most with ruby corundum, amphiboles, plagioclase, and micas. "Greenlandite" is a fuchsite-rich quartz, the geologically-oldest gemstone in world. Glossy black tourmalines were also well-known by 1813 and used as gems. Large pink/blue corundums have been found. Monazite is found in a biotite-rich pegmatite. The middle proterozoic alkaline complexes in south Greenland are of the greatest mineralogical interest. A basaltic extrusion occurred near the same time as the Gardar(?) alkaline intrusions (about 10), including the Ilimaussaq intrusion, which has an outer rim of syenite and a main body of undersaturated syenites (3 main types of nepheline syenite). This intrusion is split by Tunugdliarfik fjord. The southeast tip and northwest tip have the most interesting pegmatites. Tetranatrolite found there was thought to be natrolite until very subtle differences were noted in X-ray studies. Tugtupite forms pseudo-cubic (3 interpenetrating tetragonal pyramid-terminated prisms at right angles) and pseudo-trigonal twins. While tugtupite is normally a raspberry red after exposure to sunlight, a dark red variety has also been found. Tugtupite has been used in jewelry, as evidenced by the ~1" cabochon in Dr. Petersen's exhibit. Cryolite mining is only or one of few successful mines in Greenland; the mine was already in use in aluminum manufacture when in 1886 the electrolysis-in-cryolite method was discovered. Mining accelerated. Recently, mining has ceased as the cryolite was exhausted. Siderite, cryolite, and fluorite are found in a dome, underneath which is a mass of fluorite and topaz, under which is a mass of sulfides and quartz, under which is granite. Exotic minerals are found in dissolution cavities within the cryolite. Cryolithionite is found only as large (example: 17 cm) crystals in cryolite. Schumacher(?) identified a specimen as barite; later Albigore(?) found aluminum and fluorine and discovered it as cryolite. Narsarsuk is another intrusion. Spherical pockets to 1 meter produce about 60 minerals, including about 16 found for the first time. Some of these are leifite, pink albite, good Carlsbad twins of orthoclase, eudialyte, neptunite (type) with elpidite, epididymite (type) orthorhombic crystals twinned in three directions at 60 degrees, yellow narsarsukite (type), astrophyllite (type), and catapleeite hexagonal tabular crystals. Common at Narsarsuk are the rare earth carbonates synchysite (with calcium), cordylite (with barium), and ancylite (with strontium). Later, in the tertiary, lava flows produced native iron in west Greenland, and the Gardiner (?) complex (which includes carbonatites) in east Greenland and Disko island. Lead minerals are found in association with the iron, as are magnetites in unusual habits, gemmy titanites, and perovskites (often the first to crystallize, thus well developed, in octahedral habit). After the talk, Dr. Petersen remarked that the red visual-light color of tugtupite does not entirely return after being cycled between white and red (darkness makes the tugtupite white, light and UV make it change to raspberry red, a reversible color change called tenebrescence). –Doug Beryllite SW fluor: gray-green LW fluor: State: City: Ilimaussaq County: Mine: Okenite SW fluor: dim yellowish-white LW fluor: State: City: Godhavn County: Mine: Polylithionite SW fluor: greenish-yellow LW fluor: State: City: Kangerduarsuk County: Mine: Prosopite SW fluor: blue-white,sky-blue LW fluor: blue-white,sky-blue State: City: County: Mine: Sorensonite SW fluor: LW fluor: white,blue-white State: City: County: Mine: Tugtupite SW fluor: cherry-red LW fluor: orange State: City: Julianehaab district County: Mine: