166 GURHOLITE. 



in veinf? traversing Serpentine; whence the 

 name Gurlwfian. 

 Brit. Mus'., Case 47. 



GuRiiOLiTE, Anderson. See Gyrolite. 

 GuYACANiTE, F. Field.. A variety of 

 Enargite, from the Cordilleras of Chili. H. 

 3-5 to 4. S.G. 4-39. 



Name. The name Guyacanite was given 

 to this variety in consequence of its having 

 heen first brought to the large copper-smelt- 

 ing works of Guyacana. 



GuYAQUiLLiTE, James, F. W. Johnston. 

 An acid-resin. Amorphous. Colour pale 

 yellow, with a lustre not resinous, or imper- 

 fectly so. Opaque. Yields easily to the knife, 

 and may be rubbed to powder. S.G. r092. 

 Camp. C20 H13 0^ = carbon 76-665, hydro- 

 gen 8-174, oxygen 15-161 = 100. 



Very slightly soluble in water, and largely 

 in alcohol, giving a yellow solution, which 

 has an intenseh/ bitter taste. 



Melts at 157° Fahr., but remains viscid, ] 

 and does not flow easily until heated to 

 nearly 212°. The action of liquid ammonia 

 on this substance is very characteristic : the 

 pale yellow solutions, by the addition of a 

 lew drops of ammonia, becoming gradually 

 dark, and ultimately dark brownish-red. 

 Locality. Guyaquil, in S. America. 

 Guyaquillite, like Amber, is probably of 

 vegetable origin ; it occurs on the site of 

 ancient forests of resiniferous trees. 



Gymnite. The name given by Thomson 

 to Deweylite, from yviu-vo;^ naked, in allusion 

 to the localit}', Bare Hills, Maryland, U.S. 

 Analysis^ from Bare Hill, by Thomson : 

 Silica . 

 Alumina 



Peroxide of iron . 

 Magnesia 

 Lime . 

 Water . 



40-16 



. trace 



. 1-16 



. 36-00 



. 0-80 



, 21-60 



99-72 



Hausmann. 



Gyps, Jameson, Haidinger, 

 Gypsum, Kirwan, Phillips. 



Comp, Bihydrated sulphate of lime, or 



Ca S + 2H = lime 32-56, sulphuric acid 46-51, 

 water 20-93 = 100. 



There are several varieties of Gypsum, 

 which are described under their respective 

 names. The transparent crystals are called 

 Selenite, the fibrous varieties Satin Spar, 

 and the fine massive kinds Alabaster. See 



also SCHAUMKALK. 



Satin Spar and Alabaster are manufac- 

 tured largely into ornamental articles, and 

 works of art. Gypsum is also used in the 

 manufacture of glass and porcelain, and the 



GYPS. 



coarser kinds are employed in agriculture 

 as a top-dressing for grass-lands. Perhaps, 

 however, the largest consumption of Gyp- 

 sum is in the form of Plaster of Paris (or 

 stucco), a name which is derived from the 

 circumstance of its being found in large 

 quantities in the Paris Basin. 



Gypsum loses its water far below a red 

 heat, splitting into layers, and crumbling to 

 a white powder, which is Plaster of Par-is. 

 Moderately burned Gypsum, when ground 

 up and mixed with water, forms a paste in 

 the first instance, but this quickly hardens 

 (into what is called stucco), heat being 

 evolved, and the water passing into the 

 solid condition of water of crystallization. 

 The harder the Gypsum is before it is burnt, 

 the more solid it becomes when subsequently 

 mixed with water. 



Localities. — English. Staffbrdshire ; Not- 

 tinghamshire ; Chellaston Hill, and else- 

 where, in Derbyshire ; on the coast of 

 Glamorganshire, as well as in the cliff's 

 between Pennarth and Lavernock; in the 

 New Red Marl of tliose counties, and in the 

 salt districts of Cheshire and Worcester- 

 shire. It occurs also in the New Red Marl 

 of the vicinity of Watchet, in Somerset- 

 shire, Avhere it is occasionally collected on 

 the coast, and sent to Bristol, Swansea, and 

 some other places in the Bristol Channel. 

 The Isle of Purbeck, in Dorsetshire, 

 forming large concretions in the Lower Pur- 

 beck Beds. — Foreign. France, in the lacus- 

 trine basins of Avu^ergne and Aix, in the 

 latter containing an admixture of eight per 

 cent, of carbonate of lime ; in the fresh-water 

 clays of the Paris basin, at Montmartre, 

 Pantin, &c., with Sulphate of Strontia. 

 Spain : near Madrid, in tertiar}^ clays, ac- 

 companied by beds of Chert and of Magne- 

 site ; abundantly in the sandstones under- 

 lying Jurassic limestones both near Malaga 

 and near the Sierra Nevada, in Andalusia. 

 The Alps and Pyrenees, interstratified with 

 crystalline schists. Switzerland, at Bex. 

 The south foot of the Harz : Salzburg salt 

 formations in Austria. Sicily Avith Sulphur. 

 Italy, at Pomarance, Matarano, and Jano, 

 in Tuscany, where Serpentine is found 

 piercing limestones. Bologna, in miocene 

 clays with flints, sulphates of baryta, and 

 strontia, together with Pyrites and Sul- 

 phur. Algiers, associated with crystalline 

 limestone, gneiss, Araphibolite, and Serpen- 

 tine. Sweden, at Fahlun, associated with 

 Dolomite and Serpentine in the chloritic 

 bands of the oldest crystalline rocks of 

 Scandinavia. Asia Minor. Nova Scotia, in 

 rocks of the carboniferous series, with sul- 



