DOG'S-TOOTH SPAR. 



■ DODECAHEDRAL GaRNET BlENDE, 3Iohs. 



See Blende. 



DoDECAHEDRAL Iron Ore, Mohs. See 

 Franklinite. 



DoDECAHEDRAL KoUPHONE SpAR, Mohs. 

 See SODALITE. 



DoDECAHEDRAL Mercury, Mohs. See 

 Native Amalgam. 



Dog's-tooth Spar. The name given to 

 certain crystals of Calcite, from their fancied 

 resemblance to the tooth of a dog. They 

 have been found principally at Ecton, in 

 Staffordshire, and in Derbyshire. Fig. 166. 



Fig. 166. 



Dolomie, Leymerie. Dolomite. The 

 name applied to white crystals and granular 

 varieties of carbonate of lime and carbonate 

 of magnesia. H. 3-5 to 4. S.G. 2-95 to 3-1. 



Fig. 167. 



Fig. 168. 



Fig. 169. 



Comp. Ca C+Mg C = carbonate of lime 

 54-35, carbonate of magnesia 45 -65 = 100-00, 

 but carbonate of iron or carbonate of man- 

 ganese, or both together, are generally pre- 

 sent, 



BB like Calcite ; some varieties become 

 darker and harder. 



Soluble in acid, but more slowly than Cal- 

 cite. 



Localities. Crystallized at Leadhills, in 

 Lanarkshire (Jig. 167). Jena, &c. ; also 

 in the United States, at Richmond co., New 

 York, and at Hoboken, New Jersey, Matea, 

 a coral island near Tahiti. Granular Dolo- 

 mite or magnesian limestone is found in the 

 Pyrenees, Saxony, France, Sweden, and in 

 Somersetshire, Yorkshire, Nottinghamshire, 



DOMEYKITE. 117 



&c. ; at Building Hill, near Sunderland, it 

 forms globular and radiated earthy-like 

 concretions; and at Marsden, in the same 

 neighbourhood, a schistose Dolomite, of a 

 pale brownish-yellow colour is found, which, 

 when split into thin pieces, is very flexi- 

 ble. This quality is supposed to be owing 

 to the water it contains, as it is nearly lost 

 when the stone dries. 



Dolomite is said to be best suited for a 

 building-stone, when it has a crystalline 

 structure. 



Name. After Dolomieu, the geologist. 



For varieties of Dolomite, see Pearl Spar, 

 Brown Spar, Ankerite, Miemite, Gurhofite, 

 and Brossite. 



Brit. Mus., Case 47. 



M.P.G. Horse-shoe Case, No. 438 (cry- 

 stals) ; No. 215 (granular). 



Dolomite Sinter, v. Kohel See Hydro- 

 dolomite. A variety of Hydromagnesite, 

 with part of the magnesia replaced by lime. 

 It occurs on Somma, in isolated globular 

 or stalactitic earthy masses, resembling Sin- 

 ter, and of a white' or yellowish colour. 



Comp. According to Rammelsberg 3[(Mg, 



Ca)C + H]+MgH. 



Analysis by v. Kobell: 



Carbonic acid . . . 33-10 



Lime 25-22 



Ma:<nesia .... 24-28 



Water 17-40 



100-00 

 Dolomite Spar, Jameson. See Bitter 

 Spar. 



DoLOiNHTic Ophiolite. The name given 

 by T. Sterry Hunt to the varieties of Ser- 

 pentine which contain intimate admixtures 

 of Dolomite. 



DoMEYKiTE, Haidinger. Occurs reniform 

 and botryoidal ; massive and disseminated. 

 Colour tin-white; often with a slightly 

 yellowish or iridescent tarnish. Lustre 

 metallic. Fracture uneven. Also black and 

 soft, soiling the fingers, when impure or de- 

 composed. See CoNDURRiTE. H. 3 to 3-5. 

 S.G. 4-5. 



Fig. 170. 



Comp. Arsenide of copper or -C-u^ As' 

 =copper 71-63, arsenic 28-37 = 100-00. 



Analysis, from Calabazo in Chili, by 

 Domeyko : 



i3 



