L I M E. 



rf England'; the crylb's that exhibit its planes frequently 

 accompany ftalaclitical carbonate of lime. 'Die complete 

 dodecahedron has not yet been found. 



5 1 . Acute pyramidnl iloJnahcJron of 14° 30'. — The planes 

 of the very acute pyramids of tliis modification are of rare 

 occurrence ; and in its complete ibue the dodecahedron has 

 not been feen at all. The cryilals from Dcrbylhire, en 

 which its planes have been obferved, are the refults, fome 

 of fix, others of leven and eleven, different modifications. 



53. Acute pyramidal iloJucahcdron of 18° 26 . — Though this 

 and the two following dodecaliedrons are, like ihofe of the 

 preceding modifications, the reiult of an intermediate decre- 

 ment of the cryftalline lamince on the acute angles of the 

 planes at the bafc of the primitive rliomboid, yet they differ 

 from the latter in the cleavage, which takes place on their 

 more obtufe edges. This dodecahedron has not yet been 

 found in its complete ftate ; in combination with the planes 

 of feveral other'modifications, of which thofe of No. 36 are 

 the molt confiderable, it is found in Derbyfhire 



5 5 . Acute pyramidal dodccahcdnn of 16 $^ '. — M. de Bour- 

 nonhas obferved the planes of this modilication only in two 

 cryllals from Saxony, where they fometinics accompany 

 red filver ore. This is undoubtedly the fcarcefl; of all mo- 

 difications of calcareous fpar, and one of the few that are 

 not found in England. 



54. Acute pyramidal dodecahedron of 14° 4'. — This is the 

 moll acute of all dodecahedrons hitherto obfervedincalcareous 

 fpar. It differs but little in this refpeft from that of No. 5 1 ; 

 but independently of the confiderable diffe.-cnce in the re- 

 fpeftive inclination of their planes to each other, the cleavage 

 of the former is on the lefs obtufe edges, while that of this 

 modification takes place on the moll 'obtufe edges. M. de 

 Bournon has obferved the planes of this modification in two 

 varieties only ; the one is the dodecahedron in its complete 

 Hate ; the other exhibits its planes combined with thofe of 

 'Ho. 13, which latter happens to be the moll acute of all 

 rhomboids hitherto obferved of this fubllancc. Both 

 varieties were found in Weftmoreland. 



5 J. Acute pyramidal dodecahedron o/"34^i2'. — This dode- 

 cahedron, like thofe of Nos. 25 and3 1, iscompofedof ifofcelcs 

 triangles. Count Bournon has obferved this rare modifica- 

 tion in a few cryllals from Derbyfhire, in combination with 

 the planes of the primitive rhomboid, and thofe cf Nos. 2 

 and 4. 



IV. Dodecahedral prifmatic Alodiftcation. 



c6. Dodecahedral prifm formed at the folid angles of the lafe. 

 (not before defcribed) Its planes arc produced by a retro- 

 gradation of the cryilalline laminse on the folid angles, fo a.s 

 10 replace each of them by two planes which meet under an 

 ann^leof 142 1' ■ Its planes are found combined with thofe 

 of the hexahedral prifm No. 2, which give the cryftal the 

 form of a prifm of 18 fides; in other cryllals which, be- 

 fidesthejufl mentioned planes, cchnprife alfo thofe of No. i, 

 the prifm is compofed of 24 fides. It has been likewife 

 found in combination with the planes of fix different modifi- 

 cations, four of which belong to dodecahedrons, one to the 

 prifm of No. 2, and one to No. 56, producing in all 66 

 planes. Another variety has been obferved by count 

 Bournon, which, in addition to the planes of the lall-men- 

 tioned variety, contains alfo thofe of the prifm No. I, and 

 is confequently compofed of 72 planes. This modification, 

 wl ich has been found in Cumberland, is rare, but it is not 

 improbable that its planes may be thofe of feveral of the 

 curvilinear x-arieties already mentioned, but which cannot be 

 determined by the goniometer. 



Tiie cryftals of calc*reous fpar are varioufly aggregated, 



and often fo deeply imbedded, that their fummits only are 

 vifible. They occur of all degrees of magnitude, from mi- 

 nute to 14 inches in length ; their furfacc is generally fmooth, 

 fometimes flreaked or drufed. Externally from fiiining and 

 fplendent, to dull, fometimes pearly ; internal luihe from 

 fplendent and fpccularly fplendent, to fhining ai/d gliilening ; 

 it is nioilly a vitreous lullic, the intenfity of which is gene- 

 rally in proportion with the tranfparency of the cryftal. 



Fracture foliated, rarely curved foliated ; fragments 

 rhomboidal. The maffive is generally found in large-grained 

 diftinft concretions, but alfo fometimes in lellaceous, wedgt- 

 fhaped, and diverging, more or lefs flreaked prifmatic ctiu- 

 cretions. 



Tranfparency both of mafTue and cryftallizej calcareous 

 fpar is various ; the former is however generally only tranflu- 

 cent, while the cryflals are mollly femi-tianfparent and 

 tranfpareiit ; and thefe poffefs the double refratlion in a high 

 degree. 



It is femi-hard, between gypfum and fluor fpar, or, (ai 

 count Bournon charadlerifes its hardnefs,) jull Icratched 

 by common brafs. It is brittle, eafily frangible. 



Specific gravity 27.17 as a mean. Bourn. 



Some varieties, efpecially that of brownilh-yellow colour, 

 and part of thofe found in the fhell marble of Derbyfliire, 

 are pholphorefcent when laid on a hot coal. The fame qua- 

 lity has been obferved, by Schumacher, in varieties from Nor- 

 way. 



Its chemical charaflers agree with thofe of the preceding 

 fub-fpecies. The purell Iceland fpar is compofed of 

 Lime 55,0 55.5 



Carbonic acid 34.0 44. 



Water ii.o o.i 



100 Bcrgm. 100 



~ f Phillips Phil. 

 1 Mag. xiv. 



This fub-fpecies is found in motl parts of the world ; but 

 mod abundantly it occurs in England (where almoll all 

 modifications have been found), in Saxony and France. 

 Certain cryflal-forms appear to be peculiar to certain coim- 

 tries or localities ; but this requires farther obfervations. 



With regard to the Iceland fpar it ihould be remarked, 

 that this very pure mafTive variety of calcareous fpar, is far 

 from being peculiar to that ifland ; at Pergine, in Italy, as we 

 are told by Buch, the fame occurs in mica flate, as nialTes 

 fufTiciently large to be cleft into rhomboids of upwards of 

 two feet in length. 



Calcareous tpar is, almofl without exception, the pro- 

 duftioii of particular repofitorics ; it is never feen to form 

 independent beds or flrata. It occurs vcnigenons in the 

 rocks of almofl all formations ; in the oldell ; in Switzerland 

 and the Pyrenees, it is accompanied with feldfpar, rock- 

 cryftal, &c. Alfo frequently in various metalliferous veins 

 in gneifs, mica Dale, clay flate, fienite, porphyry, more 

 feldom in granite, frequently in granwacke, and with ores 

 of cobalt and copocr, in the older fietz lime-flone. The 

 newer fle'z lime-iione is fometimes travcrled by veins entirely 

 compofed of calcareous fpar. 



The minerals ufually accompanying calcareous fpar are 

 granular and comoaft lime-llone, brown fpar, quart/., feld- 

 fpar, barytes, fluor fpar, clay fiate, chlorite, iron and cop- 

 per pyrites, fpathofe iron, brown iron-flone, galena, blende, 

 grey copper ore, malachite, &c. 



3 . Fibrous limeflone. 



Thi.s fuh-fpecies is divided into two kinds, a, common, and 

 b, flalaftitical fibrous lime-ftone (Kalkfinter, Wern.) 



A. Common fhrous Umeflone Cemeiner fafriger kalljleiny 

 Wern. Satin fpar. 



Its 



