502 



Oryctogno- 



Granular 

 Heavy- 

 Spar. 



Curved 

 Lamellar 

 Heavy- 

 Spar. 



THIRD SUBSPECIES. 

 GRANULAR HEAVY-SPAR, Jameson. -Kornigcr 



Schwerspath, Werner. 



External Characters Colours white, and sometimes 

 ash-grey. Occasionally spotted brown and yellow on 

 the surface. Occurs massive, and in fine granular con- 

 cretions, which are sometimes so minute as scarcely 

 to be discernible. Internally glistening, approaching 

 to shining, and pearly. Fragments indeterminate an- 

 gular, and blunt-edged. Feebly translucent. Soft. 

 Rather brittle, and easily frangible. Specific gravity, 

 4.300, Klaproth. 



Constituent Parts. Sulphate of Barytes, 90 



Silica, . . 10-100 



Geognostic Situation. Occurs principally in beds, 

 along with galena, blende, copper-pyrites, and iron- 

 pyrites. . 



Geographic Situation. It occurs in beds, along with 

 galena, blende, copper-pyrites, and iron-pyrites, at 

 Peggau in Stiria ; also in the Hartz, in beds, along 

 with copper and iron pyrites, galena, and blende. 



MINERALOGY. 



rally massive ; also in distinct concretions, which are Oryctogno- 

 straight and thin lamellar; and again collected in- ._ r _'*' _. 

 to others which are coarse granular ; and also crys- 

 tallized. The following are the secondary figures it 

 exhibits : 



1. Rectangular four-sided table. 2. Oblique four- 

 sided table. 3. Longish six-sided table, -t. Eight- 

 sided table. 



Crystals vary in size, from large to small ; and rest 

 on one another, or intersect one another. Externally 

 they are smooth and splendent ; internally shining 

 and splendent, and the lustre intermediate between 

 resinous and pearly. Fragments tabular and rhomboi- 

 dal. Translucent, or transparent, and refracts double. 

 Brittle, and easily frangible. 



Chemical Characters. It decrepitates briskly before 

 the blowpipe, and, by continuance of the heat, melts 

 into a hard white enamel. 



Constituent Parts. Sulphate of Barytes, 97.60 



Sulphate of Strontian, 0.85 



Water, . . 0.10 



Oxide of Iron, . 0.80 



Alumina, . . 0.05 



Straight 

 Lamellar 

 Heavy- 

 Spar. 



Fresh 



Straight 



Lamellar 



Heavy. 



Spar. 



FOURTH SUBSPECIES. 



CURVED LAMELLAR HEAVY-SPAR, Jameson. 



Krummschaaliger Schwerspath, Werner. 



External Characters. Principal colours white, grey, 

 and red. Sometimes several colours occur together, 

 and arranged in broad stripes. Generally occurs mas- 

 sive, more frequently reniform, and long globular, 

 with a drusy surface; the drusy surface is formed of 

 very small, thin, and longish four- sided tables ; also 

 in reniform curved lamellar concretions, which are fre- 

 quently floriform, and these are again composed of 

 prismatic concretions. It is rarely marked with cubi- 

 cal impressions. Internally intermediate between 

 shining and glistening, and the lustre pearly, inclining 

 to resinous. Fracture curved foliated, which some- 

 times incline's to splintery, and thus approaches to the 

 compact subspecies. Fragments indeterminate angu- 

 lar, and rather blunt-edged. Translucent on the edges. 

 Brittle, and easily frangible. Specific gravity, 4.307, 

 Bre'dhaupl. 



Geognostic and Geographic Situations It is one ot 

 the most common subspecies of heavy-spar. In Scot- 

 land, it occurs in trap and sandstone rocks : in Derby- 

 shire, it occurs in secondary limestone : it characterises 

 a particular venigenous formation at Freyberg in Sax- 

 ony, where it is associated with radiated pyrites, ar- 

 "entiferous galena, brown blende, calcareous-spar, and 

 fluor-spar. It occurs in Sweden, Carinthia, and other 

 countries. 



FIFTH SUBSPECIES. 

 STRAIGHT LAMELLAR HEAVY-SPAR. 



It is divided into three kinds, viz. Fresh Straight 

 Lamellar Heavy-Spar, Disintegrated Straight Lamellar 

 Heavy-Spar, and Fetid Straight Lamellar Heavy- 

 Spar. 



First Kind. 



FRESH STRAIGHT LAMELLAR HEAVY-SPAR, Jame- 

 son. Geradschaaliger Schwerspath, Werner. 



External Characters. Colours white, grey, black, 

 blue, green, yellow, red, and brown. Occurs gene- 



Klaproth, Beit, b. ii. s. 78. 



Geognoilic Situation. It is found almost always in 

 veins, which occur in granite, gneiss, mica-slate, clay- 

 slate, greywacke, limestone, and sandstone. It is often 

 accompanied with ores, particularly the flesh-red va- 

 riety, and these are, native silver, silver-glance or sul- 

 phuretted silver, copper-pyrites, lead-glance, white 

 cobalt-ore, light red-silver, native arsenic, earthy co- 

 balt, cobalt-bloom or red cobalt, antimony, and manga- 

 nese. It occurs sometimes in beds, and encrusting the 

 walls of drusy cavities. 



Geographic Situation. In this island, it occurs in 

 veins m different primitive and transition rocks, and 

 also in secondary limestone, sandstone, and trap. 

 Beautiful crystallized varieties are found in the lead- 

 mines of Cumberland, Durham, and Westmoreland. 



Second Kind. 



DISINTEGRATED STRAIGHT LAMELLAR HEAVY-SPAR, nisinte- 

 Jameson. Mulmicher oder murber geradschaaliger. grated 

 Schwerspath, Werner. Straight 



Lamellar 



External Charactert Colour white. Occurs mas- H eavy. 

 sive. Glistening aad pearly. Opaque, or faintly trans- Spar. 

 lucent on the edges. Very easily frangible. Other 

 characters same as the preceding. 



Geognoslic and Geographic Situations. It was for- 

 merly met with in considerable quantity at Freyberg 

 in Saxony, in a mixture of galena, blende, and iron- 

 pyrites. 



Third Kind. 



FETID STRAIGHT LAMELLAR HEAVY-SPAR, or HE- r etl( j 

 PATITE, Jameson. Straight 



External Characters. Colours white, grey, and black. H y " 

 Occurs massive, disseminated, and in globular or el- spar, or 

 liptical pieces, from an inch to a foot and upwards in Hepatite, 

 diameter ; also in lamellar concretions, which are ge- 

 nerally straight, sometimes curved and floriform ; 

 sometimes there is a tendency to wedge-shaped and 

 radiated concretions. Externally feebly glimmering ; 

 internally shining, and intermediate between pearly 

 and resinous. Fragments indeterminate angular, and 

 blunt-edged. Opaque, or translucent on the edges. 



