DATHOLITE. 

 two inches across, cutting through the 

 porphyritic claystones which form the moun- 

 tain range at that place. 

 j Name. Named by David Forbes after 

 I Charles Darwin, in honour of his geological 

 : examination of the part of South America 

 I where the mineral occurs. 

 ! Datholite, Phillips, Dana, Brooke §• Mil- 

 I ler; Datholith, IVer.uer; Datolitb ; Da- 

 [ TOLITH, Haidinger, Hausmann, v. KobelL 

 j Oblique ; primary or cleavage-form an 

 oblique ihombic prism (Senarmont). Occurs 

 j crystallized in rhombic prisms, of which the 

 \ lateral edges and solid angles are commonly 

 ! replaced by planes ; also massive. Colour- 

 less, or inclining to greyish, greenish-white, 

 or yellowish-grey. Translucent. Lustre vi- 

 i treous. Streak white. Brittle. Fracture 

 uneven to imperfectly conchoidal. H. 5. to 

 5-5. S.G. 2-9 to 3-4. 



140. " Fig. 141. 



Borate and silicate of lime, with 



one atom of water, or Ca B + Ca 2bi + H. 

 Analysis from Andreasberg, by Rammels- 



berg : 



Silica 38-477 



Lime 35-640 



Boracic acid . . . i:0-315 

 Water .... 5-668 



100-000 



In a matrass yielr'^s water. Becomes 

 opaque and friable in the flame of a candle. 



BB swells up and melts readily to a co- 

 lourless glass, imparting at the same time a 

 green tint to the flame. 



Dissolves readily in nitric acid, leaving a 

 jelly of silica. 



Localities. — Scotch. In basaltic green- 

 stone, on the Kilpatrick Hills, in Dumbar- 

 tonshire. In the trap of Salisbury Craigs, 

 Edinburgh. Costorphine Hill, Laiiar-kshire. 



Glen Fay Perthshire, Jig. 141 Foreign. 



Arendal in Norway. Uto in Sweden. An- 

 dreasberg ; near Wolfstein, in Rhenish Ba- 

 varia. In large, transparent crystals at Monte 

 Catini, in Tuscany, and Toggiana, in Mo- 

 dena. In large, pellucid crystals at Roaring 

 Brook, 14 miles from New Haven, Connec- 

 ticut ; in nodules, like the most close-grained 



DAVYNE. 105 



marble at Minnesota Mine, Lake Superior, 

 U.S., &c. 



Name. From ^ocBos, turbid, in allusion to its 

 want of transparency. 



The synonym Datolite is derived from 

 dario/Licii, to divide ; because of its division 

 into granular portions. 

 Brit. Mus., Case 39. 

 31. P. G. Horse-shoe Case, No, 1095. 

 Daurite. See Toijrmaline. 

 Davidsonite, Richardson, Thomson. A 

 variety of Beryl, occurring in greenish-yel- 

 low crystals, near Aberdeen at the granite 

 quarry of Rubislaw, and at Tory, on the 

 south side of the Dee. Texture foliated. 

 Analysis by Heddle : 

 Silica . 

 Alumina 

 Glucina 

 Magnesia 

 Protoxide of iron . 

 Water . 



67-70 



15-64 



12-52 



3-10 



0-25 



0-lG 



99-27 

 Name: After the discoverer, Dr. Davidson, 

 Professor of Natural History in the Maris- 

 chal College, Aberdeen. 



D A VINA, Monticelli §- Covdli. See D avyne. 

 Davite, 3IilL Occurs massive of a white, 

 green, or yellow colour, the changes of colour 

 indicating some changes in the composition. 

 The yellow variety contains sulphate of iron, 

 the green sulphate of copper also, but the 

 white is solely sulphate of alumina. The 

 fracture under the lens exhibits a multitude 

 of fine silky crystals, resembling those of 

 sulphate of quinine. Taste nauseous and 

 highly astringent. 



Comp. Native sulphate of alumina. 

 Analysis : 



Extraneous substances . . 3*2 

 Sulphate of alumina . . 38-0 

 Sulp'iate of iron . . .2-4 

 Free sulphuric acid . . 4-6 

 Water 51-8 



100-0 

 BB on charcoal gives off water, sulphurous 

 and sulphuric acids, and ultimately becomes 

 a white powder Very soluble in water, 

 leaving a little impurity undissolved. 



Locality. Near a thermal spring, which 

 contains free sulphuric acid, at Chiwachi, an 

 Indian village in the Andes, one day's jour- 

 ney from Bogota, in Columbia. 



Name. In honour of Sir Humphry Davy„ 



Davyne, Allan, Phillips ; Davytic Kou- 



PHONE Spar, Haidinger. A variety of Nephe- 



line occurring in the older lavas of Vesuvius, 



