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The following phosphates of manganese are found occurring naturally.
Triplite. Orthorhombic, imperfectly crystalline. H.55.5. G. 3.44—3.88. Lustre, resinous, inclining to adamantine. Colour, brown to black. Streak, yellowish grey or brown. Subtranslucent to opaque. Composition, a phosphate of manganese and iron containing lime, magnesia and fluorine. Found at Limoges, in France, with apatite, and in Silesia. Zwieselite, a brown variety, has been found near Zwiesel, in Bavaria, in quartz.
Triphylite or Triphylin. Orthorhombic and massive. H. 5. G. 3.54--3.6. Colour, greenish grey, also bluish, often brownish black externally. Translucent in thin fragments. Composition, a phosphate of iron and manganese, containing lithia and occasionally lime, potash and soda.
It occurs in Bavaria, Finland, and at Norwich, Massachusetts.
Heterosite and Hureaulite may be considered as varieties of triphylin.
The phosphates of manganese yield more or less water when heated in a closed tube, and before the blowpipe fuse very easily to a globule and colour the flame. Those free from lithia, give a bluish green phosphoric acid flame, the others produce a lithia colouration at the same time. With fluxes they react for manganese and iron.
A silicate of manganese is found occurring naturally as Rhodonite, which occasionally crystallises in forms belonging to the triclinic system, but which usually is massive. H 5.56.5. G. 3.4–8.68. Lustre, vitreous, pearly or dull. Usually pink or rose coloured, occasionally reddish brown. Transparent to opaque.
Bustamite is a variety containing 9% to 15 % lime, which replaces part of the manganese. It often contains carbonate of lime. Colour, greyish red.
Fowlerite, contains zinc and occurs in crystals and foliated.
Rhodonite is fusible in the reducing flame to a reddish glass, in the oxidizing flame to a black metallic globule, and is unacted upon by acids. It is found in Sweden, the Harz, the Ural and in Cornwall.
There are two native sulphides of manganese ; the first, a monosulphide known as Alabandite, Manganblende, or Vanyanglanz contains Mn=63.3 % S=36.7 % Colour, blk. Streak green. It is found in Transylvania. The second, Hauerite is a disulphide. Mn=46.3 % S=53.7%. Colour, reddish brown, It has been found at Kalinka in Hungary.
Manganese is found associated with the metal tungsten in the minerals.
Wolframite, a tungstate of iron and manganese.
Megabasite, a tungstate of manganese containing a little iron.
Among other manganese minerals are Crednerite, an oxide of copper and manganese; Franklinite, an oxide of iron, zinc and manganese; Chondrarsenite, occurring at Paisberg, in Sweden, as yellow grains in barite, probably an arseniate of manganese. Sussewite, found on Mine Hill, Sussex Couny, New Jersey, associated with franklinite, zincite and other manganese and zinc minerals, is a borate of manganese and magnesia. Manyanese alum or dpjuhnite has been found on the shores of the Great Salt Lake, and a manganese and magnesium alum in the Canton Uri, Switzerland.
Such is a brief review of the principal ores of manganese, and though few possess economic value, yet a certain amount of interest must attach itself, even in practical miuds, to tie less useful members of a family which possess relations of such commercial importance as pyrolusite, psilomelane, manganite and wad.
Field Meeting, September 8th, 1883.
Held at Speke. Conducted by Mr. T. S. KEYTE. The section of Pebble Beds extending to north of the station was examined. Afterwards, the party inspected a cutting in the Boulder Clay to the south of the railway bridge, in which some good examples of boulders containing hornblende crystals and a few shells were found.
Visit to the Museum, September 22nd, 1883.
Conducted by Mr. F. P. MARRAT, who exhibited and described the Philip's Collection" of Minerals, opened to the members by permission of Mr. T. J. MOORE, the Curator. Mr. MARRAT explained the unique character of the Collection, which comprises the actual specimens from which Philips wrote his celebrated works on Mineralogy.
END OF VOLUME III.