498 



MINERALOGY. 



Oryctogno. Geographic Situation It is found at the mine nam- 

 i__*'-_^ ed Segen Gottes -at Gersdoi-f in Saxony ; and in that of 

 ""Y" \'alenciana at Guanauxuato in Mexico. 



IV. RHOMB-SPAR, Jameson. Langaxiges Kalk-Ha- 

 loid, Mohs. 



Rhomboid=106 8 15' Cleavage rhomboidal. Hard- 

 ness=3.5 4.0. Sp. gravity=2.8, 3.2. 



External Characters Colours white, grey, and yel- 

 low. Occurs massive, and disseminated ; and crystal- 

 lized in rhomboids, in which the obtuse angle is 106 s 

 1 5'- These rhomboids are sometimes rounded or trun- 

 cated on the edges. Crystals middle-sized and small ; 

 the surface is sometimes smooth, sometimes rough, and 

 either shining or glimmering. Internally the lustre is 

 splendent, between vitreous and pearly. Fracture im- 

 perfect conchoidal. Fragments rhomboidal. Easily 

 frangible and brittle. 



Chemical Characters. Before the blowpipe it is in- 

 fusible, without addition : even when pounded it ef- 

 fervesces but feebly ; and dissolves slowly in muriatic 

 acid. 



Constit. Paris Carbonate of Lime 56.60 



Carbonate of Magnesia 42.00 98.60 

 Or by another result; Carbonate of Lime 56.2 



Carbonate of Magnesia 43.5 98.9 

 With a trace of Manganese and Iron, Murray*. 



Geognostic Situation, It occurs imbedded in chlorite 

 slate, talc-slate, limestone, and serpentine ; in the salt 

 formation, where it is imbedded in anhydrite and gyp- 

 sum ; in drusy cavities in compact dolomite, and in 

 metalliferous veins. 



Geographic Situation __ It occurs imbedded " in 

 chlorite-slate on the banks of Loch Lomond ; in a 

 vein in transition rocks, along with galena, blende, 

 copper-pyrites, and calcareous-spar, near Newton- 

 Stewart in Galloway; in compact dolomite in the Isle 

 of Man and the north of England. 



OEDEE II. BARYTE. 



No metallic lustre. Colour rarely changed in the 

 streak ; if orange-yellow, the specific gravity is 6, and 

 more. Hardness ranges from 2.5 to 5. Sp. gravity 

 ranges from 3.3 to 7.2. If the specific gravity be less 

 than 3.6; and the hardness 5, the cleavage is di-pris- 

 matic. 



GENUS I.RED MANGANESE. 



RED MAN- One ax i s - Cleavage rhomboidal. Hardness:=3.5, 

 GANESE. " 4.5. Sp. gr.=3.3, S.f). 



This genus contains one species, viz. Romboidal Red 

 Manganese. 



1. RHOMBOIDAL RED MANGANESE, Jameson Lan- 

 gaxiger Flintz-Baryt, Molts. 



Rhomboid= . Cleavage rhomboidal. Hardness 

 =3.5. Sp. gravity=3.3, 3.6. 



This species is divided into three subspecies, viz. 1. 

 Foliated rhomboidal red manganese, 2. Fibrous rhom- 

 boidal red manganese, and 3. Compact rhomboidal red 

 manganese. 



FIRST SUBSPECIES. 



Foliated FOLIATED RHOMBOIDAL RED MANGANESE, Jameson. 

 ' '" External Characters. Colour bright rose-red, slightly 

 nese, inclining to flesh-red. Occurs massive, disseminated, 

 small reniform, globular, with tabular and rhomboidal 

 impressions, and in granular distinct concretions. In- 

 ternally shining, inclining sometimes to glistening, 



Order II 

 BARTTR. 



manganese, 



Fibrous 

 rhomboidal 

 red manga- 

 nese. 



sometimes to splendent, and the lustre pearly. Frag- Oryetojrno- 



ments indeterminate angular, and rather sharp-edged, 



or rhomboidal. Generally translucent on the edges ; ^"Y"'*' 



in some rare varieties translucent. Brittle, and rather 



easily frangible, 



Chemical Character Before the blowpipe, without 

 addition, it first becomes dark brown, and then melts 

 into a dark reddish-brown bead. 



Const. Parts. Oxide of Manganese 52.60 

 Silica . 39.60 



Oxide of iron . 4.60 



Lime . . 1.50 



Volatile ingredients 2.75 101.5 



Berzelius, in Afh. i. Fys. och. Min. i. 110. 

 Geognoslic and Geographic Situations. It occurs in 

 beds of specular iron-ore and magnetic iron-ore, along 

 with compact garnet and calcareous-spar, in the gneiss 

 hills at Langbanshytta, in Wcrmeland in Sweden ; also 

 at Catharinenburg in Siberia, and in Saxony. 



Uses The Siberian varieties are cut and polished, 

 and worn as ornamental stones. 



SECOND SUBSPECIES. 



FIBROUS RHOMBOIDAL RED MANGANESE, Jameson. 

 External Characfers.^Colours rose-red and flesh-red, 

 inclining to grey and brown. Occurs massive, and in 

 prismatic fibrous concretions, which are straight, scopi- 

 form and stellular. Internally glistening and pearly. 

 Fragments splintery and wedge-shaped. Feebly trans- 

 lucent. 



Geognostic and Geographic Situations Tt occurs in 

 veins in primitive and transition rocks. It is a rare 

 mineral, and is principally found at Kapnik in Tran- 

 sylvania, and at Schemnitz in Hungary. 



THIRD SUBSPECIES. 

 COMPACT RHOMBOIDAL RED MANGANESE, James. 



External Characters Its principal colour is pale 



rose-red, which sometimes passes into dark reddish- 

 white. Occurs massive, disseminated, and sometimes 

 imperfectly reniform. Internally dull or glimmering. 

 Fracture even sometimes inclining to splintery. Frag- 

 ments indeterminate angular, and rather sharp-edged. 

 Brittle, and easily frangible. 



Chemical Characters It is infusible before the blow- 

 pipe, but becomes black by ignition. 



Siberia. 



Constituent Parts. Oxide of Manganese 6l 

 Silica . 30 



Oxide of iron 



Alumina . 298 



Lampadius, in Pract. Chem. Abh. b. ii. s. 209. 



Geognostic and Geographic Situations. It occurs at 



Kapnik in Transylvania ; at Langbanshytta, in Werme- 



land in Sweden ; and Catharinenburg in Siberia. 



GENUS. 1 1 SPARRY IRON. 



KURZAXIGEII FLINZ BAHYT, Mohs Spathisenstein, 

 Werner. Fer oxyde carbonatee, Hatty. 



One axis. Cleavage rhomboidal. Hardness=3.5, 

 4.6. sp. gr.=3.6, 3.9. 



This genus contains one species, viz. Common Sparry 

 iron. 



1. COMMS SPARRY IRON, Jameson Spatheisenstein, 

 Werner. Fe.r oxyde carbonatee, Haiiy. 



Rhomboid= 1 07. The most perfect cleavage is in the 

 direction of the planes of the primitive rhomboid ; the 

 least perfect in the direction of the planes of a tfat 



Compact 

 rhomboidal 

 red manga- 

 nese. 



Ino*. 



Common, 

 sparry iron. 



* The above analysis was communicated to us by the late Dr. Murray. 



