MINERALOGY. 



and fiilphur-vcllow ; further into fiftin-green, afparagus- 

 grceii, pilhichio-grcen, leek-green, and inountain-green, 

 whicli latter pafTes into greeniHi-grey and greenilh-wliite. 



The olive-brown palTes into bhickifh-brownj pitch-black, 

 and greyifli-black. 



Befid'es occurring cryftallized, the diamond is alfo found 

 in rolled pieces and grains. The cryllalli/.ations of the 

 diamond, beiides the oftahedron and its varieties, are, the 

 perfect tetrahedon ; the tetrahedron with truncated angles, 

 or with the angles acuminated by three planes, fet on the 

 lateral planes ; fegments of the tetrahedron, either detached 

 or united, forming twin cryftals ; the rhomboidal dodeca- 

 hedron, with convex planes or faces ; the fame figure fome- 

 what elongated ; the dodecahedron, with the planes divided 

 diao-onally ; an acute double fix-fided pyramid, with the 

 lateral planes fet on each other, and the apex acuminated 

 by fix planes fet on the lateral planes ; a flat double three- 

 fided pyramid, with convex planes iit laterally on each 

 other, and the angles of the common bafe acuminated by 

 four planes fet on the lateral planes ; a flat double three- 

 fided pyramid, on which the lateral planes of the one are fet 

 on tlie lateral edges of the other, and the angles of the 

 common bafe truncated ; a fix-fided table, with oblique ter- 

 minal plates ; and lallly, the diamond has been found in a 

 cubic form, either perfeil or with the edges truncated, or 

 varioudy modified. 



The furface of the oftahedron is either fntooth or 

 ftreaked ; the external luftre of the natural diamond is 

 adamantine, and alternates from fplendent to glimmering ; 

 internally it is highly fplendent. It is feldom completely 

 tranfparent. The black diamonds are nearly opaque. 

 The diamond has a four-fold equiangular cleavage parallel 

 ■with the planes of the oftahedron in this direftion ; it is 

 ratiier eafily frangible. The diamond fcratches all other 

 minerals. Itsfpecific gravity is ftated by Mr. Lowry at 3.488. 

 The diamond, befides its other localities, is found in the 

 diftrift of Serro Dofria, in Brafil : it was firll difcovered 

 there about the middle of the laft century, in gullies of 

 torrents, and the beds of rivers, where gold is alfo obtained, 

 but for a very confiderable time, the diamonds being 

 unknown, were difregardcd and thrown away. Diamonds 

 occur alfo- in other parts of Brafil, in the rivers Giquitig- 

 nogna, Riacha Fundon, and Rio de Peixe. See Gem. 



DiASPORE is regarded as a variety of wavellite. (See 



Wavellite. ) It occurs in curved lamellar concretions 



ealdy feparable from eacli other ; it has a grey colour, a 



{hining pearly lulfre, the angular pieces cut glafs. It flies 



before the blow-pipe, but is mfufible. Its fpecific gravity 



is 3.43. According to Vauqueliu, the coniHtuent parts are, 



Alumine - - . . 80 



Water - - . - 17 



Oxyd of iron - . . 3 



A very fmall fpecimen analyfed by Vauqueliu gave forty- 

 two Jier cent, of lime. This mineral is found, according to 

 Hermann, in the land of Konguire, 125 leagues from the 

 Rufiian frontier, where it is aflbciated with malachite and 

 calcareous fpar. 



DiPVRE. See Zeolite. 



DisTHENE, or Kyaiute; Sappare, Sauffure. See Kvanite, 

 Addenda. 



Dolomite, a fpecies of magnefian lime-ftone, to which 

 the name was given in honour of Dolomieu, the celebrated 

 French Geologiil. Mr. Jamefon has clafled the different 

 kinds of magnefian lime-llone into one order, which he calls 

 the dolomite family : it contains four fpecies, dolomite, 

 brown fpar, miemite, and gurhofite. The dolomite fpecies 

 he has divided into four fub-fpecies, common dolomite, dolo- 

 m'tie fpar or rhomb fpar, columnar dolomite, and compact 

 dolomite or magnefian I'lme-Jlone. 



Common dolomite occurs in beds in primitive mountains, 

 and frequently contains tremolite. It nearly refembles 

 primitive lime-llone or ftatuary marble, the chaux carbonates 

 faccaroide of the French, but may be diftinguilhed from it 

 by the little eftervefcence which it yields on the application 

 of mineral acids compared with the former. The grains of 

 dolomite are alfo more loofely adhering than in white pri- 

 mitive lime-ftone. The mineralogical charafters of common 

 dolomite are given under the article Dolomite. Dolomite 

 generally phofphorefces when rubbed in the dark or heated. 

 The conftituent parts of different dolomites are given by 

 Klaproth as under : 



St. Golliard. Apperiones. Ciruithia. 



Carbonate of magnefia - 46.50 - 38.00 - 48.00 

 Carbonate of lime - - 52.00 - 65.00 - 52.00 

 Oxyd of manganefe - 0.25 - 



DiCHROlTE. See loLiTE, Addenda. 

 DlopslDE. See Alalite, Addenda. 

 Dioptare, Emerald Copper Ore, occurs in cryftalhzed fix- 

 fided prifms, acuminated by three planes fet on the lateral 

 edges : it is tranflucent, and fcratches glafs feebly. The 

 fpecific gravity is 3.3, Haiiy. Aecording to Luvitz, the 

 conltituent parts are, 



Oxyd of copper 



Silex - - . , 



Water .... 



55 

 33 

 12 



Oxyd of iron 

 Lofs 



■/> 



103 



100.20 



Flexible dolomite is found in the mountain of Campo 

 Longoman, St. Gothard. 



Dolomite Spar, or Rhomb Spar. See Brown Spar, 

 Addenda. 



Dolomite, Columnar, occurs in ferpentine, in a mine at 

 Mjafs, in Ruiiia, in ftraight prifmatic concretions : its colour 

 is pale greyifli-white, the lultre vitreous inclining to pearly. 

 It is feebly tranflucent. The fpecific gravity is 2.765. 

 According to Klaproth, the conllituent parts are, 



Lime . . - - 28.20 



Magnefia - - - 19.74 



Oxyd of iron - - - 0.50 



Carbonic acid - - - 39.25 



Water - - - - 11. 31 



Lofs - - - - I. 



TOO 



Dolomite, Compafl, m.agnefian hme-fl;one. See Mag- 

 nesian Lime-Jlone, Addenda. 



Egyptian Jasper. See Jasper. 



Elaolite, Fettjleen, Werner ; Piene-grajfe, Haiiy. The 

 colours of this mineral arc dark-greenifh or blueifli-grey, and 

 flefli-red ; it is tranflucent in a low degree, and has a fhining 

 refinous luftre. The blueifli varieties difplay a peculiar 

 opalefcence. It occurs maflive, and has a diltintl double 

 cleavage. The fradlure is uneven. It fcratches glafs, is 



rather 



