MINEKALOGY. 



90.9 

 9.1 



Silver.) For a more particular account of thefe repofi- 

 tories of the precious metals, we mull refer our readers to 

 the various travels of M. Humboldt, to whom we are in- 

 debted for almoft all the correti information we have re- 

 ipefting the European colonies in South America. The 

 quantity of gold and filver imported from thefe colonies 

 between the years 1492 and 1803, he iUtes at eleven hundred 

 and fixty-fix millions in pounds fterling ; an amount fome- 

 what exceeding that of the prefent national debt of 

 England ! ! 



Grammatite, Tremolite. See Tremolite. 



Grantlar Lime-Jlone, ftatuary marble ; Chaux car- 

 lonatee J'auarcide, Fr. See LiME-STONE, and Lime-stone, 

 Addenda. 



Graphic Gold and Graphic Tellurium. See Tel- 

 lurium. 



Graphite. Plumbago or black-lead, (fee Plumbago,) 

 has an iron-grey colour, and a glimmering or gliftening 

 metallic luftre. It is fediile, and when fredt cut has a lead- 

 grey colour : it is unftuous to the touch,"yields to the nail, 

 and leaves a diftindl lead-grey mark on paper. Before the 

 blow-pipe it gradually burns away, leaving a portion of red 

 oxyd of iron. According to Berthollet, the conftituent 

 parts are, 



Carbon - . . , 



Iron ... 



The graphite of Borrowdale occurs with ochreous and 

 unftuous clay ; it is found in nodules and maffes of various 

 fizes. The bed in which it is found lies in a rock of grey 

 porphyrite felfpar, which has been improperly called grey 

 wacke. Three beds of fcaly graphite have lately been dif- 

 covered in a rock of mica-flate or gneifs, near Buley, in 

 Invernefs-(hire. 



Green Earth, Chlorite •z.ograph'ique, French. This mi- 

 neral, though made a diftinft fpecies by Werner, appears 

 to be foft earthy chlorite (fee Chlorite) : it generally 

 occurs in cavities or incrufting agates in amygdaloid. It is 

 of various fhades of green, is foft and feftile, and adheres 

 nightly to the tongue. The fpecific gravity is 2.5. Before 

 the blow-pipe, it is converted into a black flag. It is ufed 

 as a green colour in water-painting. When flightly burned, 

 it affords a beautiful and durable brown. 



Grenatite, Staurotide, Hauy ; the ftaurolite of fome 

 mineralogiifs. (See Staurolite. ) This mineral is claffed 

 in the garnet family by Werner ; but it varies from garnet 

 in the form of its cryftal, which is an oblique four-lided 

 prifm, truncated on the acute lateral edges. Sometimes 

 it is bevelled on the extremities by two planes fet on the 

 lateral edges, and the edge of the bevelment is truncated. 

 The cryilals fometimes interfedl each other, forming a 

 crofs; hence it has been called crofs-ftone by fome mine- 

 ralogifts : but it is a very dillinft fpecies from the harmo- 

 tome, or crofs-ftone, which is a member of the zeolite family. 

 (See Zeolite.) The colour of grenatitc is dark reddifh- 

 brown. It is infufible before the blow-pipe. The above 

 charafters diilinguifh it fi-om precious garnet. It occurs 

 imbedded in mica-flate, and in talc, generally accompanied 

 with kyanite and precious garnet. 



Grey Antimony-Ore. (See Antimony-Ores.) Grey 

 antimony occurs in fome of the mines in Cornwall in con- 

 fidcrable quantities, particularly at St. Stephen's, Padftead, 

 and Huel bays. It is found alfo at Glendennijig, in Dum- 

 friesfhire. 



Grey Cobalt -Ore. (See Cobalt-Ore.) This mineral 

 is found at Herland and Dolcooth mines, and in fome other 

 veins, in Cornwall. 



Grey Manganefe-Ore. See Mavganese. 



Gypsum, felenite ; Chaux fulfatee, Haiiy. See Gtp- 



SUM. 



Harmotome, Crofs-Jlone. See Zeolite. 



Hauyxe, Latialite, Haiiy. A mineral claffed by the 

 German mineralogiils with the azure-ftone, or lapis lazuli 

 family. It was firft difcovered in the volcanic rocks of 

 Albano and Frafcati, and called latialite, from ancient 

 Latium, and was afterwards difcovered in the bafaltic rock 

 of Andernach, and has been called Hailyne, in honour of 

 the celebrated mineralogiil Haiiy. Haiiyne has a ficy-blue 

 colour, pafling into pale Berlin-blue and blueilh-green. It 

 occurs in imbedded grains, and cryftallized in minute fplen- 

 dent rhomboidal dodecahedrons. The frafture is con- 

 choidal, pafling into uneven ; it has a vitreous luftre, is 

 tranfparent or femi-tranfparent, fcratches glafs, and is 

 infufible before the blow-pipe. When pulverized, it gela- 

 tinizes with muriatic acid, giving out an odour of ful- 

 phuretted hydrogen. The fpecific gravity is from 3. l to 3.3. 

 According to Vauquelin, the conftituent parts are, 



Silex ----- 30.0 



Alumine . - . . \^.o 



Sulphate of lime . - - 20.5 



Potafli - - - - ii.o 



Iron ----- I 



Water .... ly.j 



95.0 



It has by fome mineralogifts been claffed with fapphire, 

 and defcribed under the name of faphirin. It was ar- 

 ranged by Cordier with fpinel. 



Heavy Spar, Sulphate of Barytes, Baro-Selenite. This 

 mineral exceeds in weight all other purely earthy minerals, 

 its fpecific gravity being from 4.3 to 4.49. It occurs 

 both maffive and cryftallized in many metallic veins. Its 

 colours are various fhades of white, yellow, red, greenifh- 

 grey, and blue. Cryftallized heavy fpar is tranfparent or 

 tranflucent, and refi-afts doubly ; it has a diftintt lamellar 

 ftrufture, and fplits into a right -rhomboidal prifm, w^hich 

 is its primitive form ; the angles of the rhomb are 

 ioii° and 78^°. The joint parallel to the bafe of the 

 rhomb is the moft diitincl. The luftre is fhining, between 

 vitreous and refinous : it yields readily to the knife. Before 

 the blow-pipe it decrepitates violently, and then melts into 

 a hard white enamel. A piece expofed to the blow-pipe, 

 and laid on the tongue, gives the flavour of fulphuretted 

 hydrogen. The powder of fome varieties of heavy fpar, 

 when calcined, aljforbs Hght, and emits it again in the 

 dark. Sulphate of ftrontian (fee Strontian) is the only- 

 earthy mineral with which heavy fpar can probably be con- 

 founded. White lead-ore may be diftinguiflied from heavy 

 fpar, as it is fofter,,and yields a metallic globule before the 

 blow-pipe. Pure heavy fpar confifts of 



Barytes . . - - 67 



Sulphuric acid - - ■ 33 



100 



Mr. Jamefon makes the following varieties of heavy fpar» 

 which he claffes as fub-fpecies : earthy heavy fpar, con:» 

 pad heavy fpar, granular heavy fpar, lamellar heavy fpar, 

 radiated heavy fpar, fibrous heavy fpar, and prifmatic heavy 

 fpar ; and he divides lamellar heavy fpar into three kinds, 

 ftraight lamellar heavy fpar, curved lamellar heavy fpar, 

 and difintegrated lamellar heavy fpar. 



4 B 2 Earthy 



