142 FLUOR. 



usually glimmering in massive varieties. 

 Streak white. Brittle; fracture more or 

 less perfectly foliated. Easily cleaved into 

 the tetrahedron, acute rhombohedron, and 

 octahedron. H. 4. S.G. 3-14 to 3-2. Mean 

 of 60 experiments by Kengott, 3*183. 



Fig. 394. 



Fig. 195. 



Fig. 196. 



Fig. 197. 



Comp. Fluoride of calcium or CaF = 

 calcium 51-3, fluorine 487 = 100. 



When pounded and placed on ignited 

 coal it exhibits a phosphorescent light, 

 which ceases at a high temperature, but 

 may be partially restored by au electric dis- 

 charge. Fragments rubbed against each 

 other in the dark become luminous. 



BB decrepitates and ultimately melts 

 without addition to an opaque greyish- 

 white enamel. 



Localities. — English. Cornwall at several 

 mines ; at Huel Cupid and North Grambler, 

 near Kedruth ; Huel Mary Ann, Menhenniot, 

 in fine blue beveled cubes; near St. Agnes in 

 translucent crystals of a rich lilac colour, ^(/s. 

 190 and 197. Other Cornish forms ai'e repre- 

 sented mfgs. 194 and 195. Cumberland : at 

 Cleator Moor, in fine, yellow, transparent 

 crystals, the prevailing colours of which are 

 lilac and greeu : at Alston in the cube and of 

 the forms shown in Jic/s. 196 and 192. A 

 variety occurs at this locality which appears 

 green by transmitted light and blue by re- 

 llected light. Crj'stals possessing a similar 

 peculiarity also occur at Weardale, in 

 Durham, but the colours exhibited by the 

 latter are grey by transmitted and purple by 

 reflected light. According to Professor Stokers 

 this eff^ect, termed by him Fluorescence, is 

 due to a peculiar refracting power of the first 

 surface on which the light falls. Cromford 

 near Matlock Baths, Derbyshire. In Derby- 

 shire compact and granular varieties of Fluor 

 are abundant : the finest specimens for orna- 

 mental purposes come from Tray ClitF, and | 



FCETID QUARTZ. 



are called Blue John. Beeralston in Devon- 

 shire, in cubic and octahedral forms, 193, 195, 

 197, 194, and 191 ; also fibrous and compact. 

 —N. Welsh. Moel-y-Cria, and Halkin Moun- 

 tain, near Holy well. — Scotch. Balater House, 

 Glenmuick, Aberdeenshire. Dumbarton ; 

 Gourock near Greenock in Renfrewshire. — 

 Irish. Several mines in Clare county. The 

 Glendalough lead-mines, both crystallized 

 and massive, of a pale violet-blue colour. — 

 Foreign. Mont Blanc and St. Gotthard ; on 

 the latter in beautiful rose-coloured octa- 

 hedrons in Dolomite. Saxony. The Bannat. 

 Munsterthal in Baden, in hexakisocta- 

 hedrons. Zinnwald in Bohemia, also at 

 Schlackenwald in green octahedrons and 

 violet-blue rhombic dodecahedrons — the 

 latter with white stripes in the position of 

 the longer diagonal. The Lombardian Alps 

 at Monte Presolana, in the Val di Scalve, 

 N.W. of Lago Pal zone, in a vein 21 inches 

 wide imbedded in the New Red Sandstone of 

 Val Torgola, a branch of Val Trompia. 



Besides the use of Blue John in the manu- 

 facture of ornamental articles, as tazzas, 

 vases, obelisks, &c.. Fluor-spar is employed 

 for etching on glass. This is effected by ex- 

 posing a plate of glass coated with wax (on 

 which the required design has been previously 

 drawn with an etching point, as in the 

 ordinary process) to the action of the gase- 

 ous hydrofluoric acid obtained by treating 

 Fluor-spar with sulphuric acid. Those parts 

 of the plate which are covered with Avax will 

 remain unaffected, but wherever the wax 

 has been removed the glass will be cor- 

 roded, and in this manner drawings on glass 

 maj' be produced without much difficulty. 



Fluor-spar is also used in considerable 

 quantities as a flux for metallic ores : hence 

 its name from the Latin fluo, to flow, or 

 probably the name may have originated in a 

 belief that it was formed ex Jiuido, or out of 

 water. 



Ozone has lately been discovered by Prof. 

 Schrotter, in the darkish blue variety of 

 Fluor, which is found at Wulsendorf. The 

 quantity was found to amount to 02 per 

 cent. 



Brit. Mus., Case 58. 



31. P. G. Vase on pedestal 35, in Hall, 

 from Derbyshire. Horse-shoe Case, Nos. 

 331 to 364. Wall-cases 27 and 30. 



Fluss-Saures Cerium, German. See 

 Fluocerite. 



FoAMi^iG Earth, Jameson. See Aph- 



RITE. 



F<ETiD Quartz, Bakewell. A kind of 

 Quartz yielding a peculiar odour of sulphu- 

 retted hydrogen when struck with a hammer 



