MINERALOGY. 



507 



Orrclofnt- veins in gneiss, in the gold mines of Bcresofsk, in the 

 y- Uralian mountains. In these mines, it is associated 

 "" Y "*' with brown iron-ore, cubes of iron-pyrites., native gold, 

 green lead-spar, galena, and quartz. 



Ute. fn KUSM.I. a very beautiful and costly orange- 

 yellow colour is prepared from it, and which is used by 

 painters. 



Pyramidal 4 PYRAMIDAL LF.\P-?PAR, or YELLOW LEAD-SPAR, 

 led-*par. Jamcton. Pyramidal Blei- Baryt, Moht. Gelb Bleierz, 

 Werner. Plomb molybdate, Many. 



Pv ramid = 99 40' ; 131 45'. Cleavage in the di- 

 rection of the faces of the pyramid, or in the direction 

 of the terminal faces of a rectangular four-sided prism. 

 Hardness = 3. Sp. gr. = 5, 6'.8. 



External Characters. Most frequent colour wax- 

 yellow. Occurs massive, in crusts, cellular ; and crys- 

 tallized in the following figures: 



1. The pyramid truncated on the angles and sum- 

 mits. 2. The pyramid so deeply truncated in all the 

 angles, and on the common base, that the original faces 

 disappear, when there is formed a regular eight-sided 

 table, which is sometimes so thick as to appear as an 

 Sometimes four of the terminal 

 edges are truncated, when a twelve-sided table is form- 

 ed. 3. Pyramid deeply truncated on the summits, and 

 on the common base, and die angles of the common 

 base beveiled, which gives rise to the rectangular four- 

 sided table, bevelled on the irnniii.il edj;es 4. Pyramid 

 truncated on the Literal edges, which gives rise to the 

 double ei^'lit-sided pyramid When thi- figure is deep- 

 ly triiii'-.t il on the summit", there U funned, .5. Are 

 gular eight- -i ' > ><-vellt d on the terminal planes. 



Tables usually broad and thin, alternate from small 

 to very small, but are seldom middle-si/ed Frequent- 

 ly intersect each other, and are often closely aggrega- 

 ted. Externally generally splendent or shining ; in- 

 ternally shining or gli-tening, and the lustre resinous, 

 inclining to adamantine. Fracture small and fine- 

 grained uneven, or small conchoidal Fragments inde- 

 terminate angular, and rather sharp-edged. Generally 

 translucent, or only translucent on the edges ; some rare 

 .-ds are semitransparent. Rather brittle, and easily 

 frangible. 



Chemical Character*. It decrepitates before the 

 blowpipe, and the.) melts into a dark greyish-coloured 

 mass, in which the globules of reduced lead are di-per- 

 sed. 



Conttiluent Part*. Oxide of Lead. 58.40 

 Molybdic Acid. 58.00 

 Oxide of Iron, 2.08 



Silica, . . O.'M 9666 

 llmrlirll, Phil. Trans, for l?y(J. 



Geocnotlic and Geographic Situation* \\ occurs at 

 BK-iberg in Carinthi;, in a compact limestone; also in 

 the Maukeriz. near Brixlegg in the Tyrol ; at Anna- 

 berg in Austria, and Rezbanya in Transylvania. 



Trl-prU- 5. Tlll-l'RI M\Tir I.EAD-SpAR.Or SULPHATE of LEAD, 



lie Iwd- JltMoon. Tri-prisinati-cher Blei Baryt, Moht. Vitriol 



utr. Plomb Sulphate, llntiy. 

 vertical pri-sn = 120*; horizontal prism in the 

 direction of the longer diagonal = 70 31' ; and in the 

 smaller I ( leavage is the same. Hardness = 



3.0. p. gr. = 



irirri Colours yellowish and greyish- 

 ish- white, occasionally stained pale-yellowish, from 

 brown iron-ochre. Occurs massive, disseminated, and 



in ongulo granular distinct concretions, but most t're- Oiyctojno. 



quently crystallized. The following are the principal s >' r 



crystallizations : 



1 . Oblique four-sided prism, acutely bevelled on the 

 extremities, and the bevelling planes set on the acuter 

 lateral edges. 2. Broad rectangular four-sided pyra- 

 mid. 



Crystals small and very small, seldom middle-sized ; 

 and occur in druses, or superimposed. Externally splen- 

 dent and shining ; internally shining, and the lustre 

 adamantine. Fracture small conchoidal. Fragments 

 indeterminate angular, and rather blunt- edged. Alter- 

 nates from transparent to translucent. Streak white. 

 Rather brittle, and easily frangible. 



Chemical Character*. It decrepitates before the 

 blowpipe, then melts, and is soon reduced to the metal- 

 lic state. 



Wadoddiesdi 



Conrtituent Part*. Oxide of Lead, 70.50 

 Sulphuric Acid, 25.75 

 Water of Crystalli- 

 zation, . 2.25 



93.9 



Kliiprolh. Beit. b. iii. s. 164. and 166. 

 Geognntlii n d (.. graphic Situalinns. It occurs in 

 veins along with galena and lead-glance, and different 

 spars of lead, at Wanlockhead in Dumfriesshire, and 

 Lead Hills in Lanarkshire; at Pary's Mine in Angle- 

 sey, and Pe.ii/.ince in Cornwall. On the Continent, it 

 i* met with at Zellerfeld in the Hart/, and in the 

 Westerwald mountains. 



CORNEOUS LEAD (a.) Jameson. Hornblei, H'crnrr. Comeoiu 



External Character*. Colours greyish-white, and yel- 

 lowish-grey, passing into pale wine yellow. Occurs cry - 

 stallized in oblique* four-sided prisms. Internally s-, 

 dent, and lustre adamantine. I las a threefold OHM 

 the cleavages parallel to the planes of the (bar-sided 

 priin. Fr-icti.rc conchoidal. More or less transparent 

 In soft; rather softer than white lend--p-.r. Is sectile, 

 and easily frangible. rWr. 



Chemical Clnrucl- rs On exposure to the blowpipe 

 or charcoal, it melts into an orange-coloured globule, 

 and appears reticular externally, and of a white colour 

 when -olid ; when again melted it becomes white ; and 

 on increase of the heat the acid flies off, and minute 

 globules of lead remain behind. 

 Coiutituent Parlt. Oxide of Lead, 85.5 



Muriatic Acid, 85 



Carbonic Acid. 6.0 100.0 



Kiaprulh. Beit b. iii. s j44. 



Groeraphi- fliliia/iiin Europe. In Cromt'ord Level 

 near Matlock in Derbyshire; and at Hausbaden, near 

 Badweiler in (nrinany. 



America. In the neigbourhood of Southampton in 

 the United States. 



*AKSFNIATE or LEAO,./OWC*O. Bleihluthe,//<iv.'in/)ii. Arteniati 



This species is divided into three subspecies, viz. ofl " d> 

 Reniform arxeniate of Lead Filamentous areeniate of 

 Lead, and Earthy arseniate of Lead. 



FIRST SUBSPECIES. 

 REMFORM ARSENIATE or it.\r>, J'imeion Blciniere, Reniform 



lliiiiMiuinn ats-mateof 



External C/taractert Colours on the fresh fracture lead< 



l , ue not jtt included in the CJcnui Lcad-ipu, u their chanctcn hue not been completljr ascertained. 



