MINERALOGY. 



Earth Heavy Spar occurs fometimes loofe, and fometimes 

 cohering in the druiy cavities in veins : it is compofed of 

 dull or glimmering dully particles, \\'hich feel meagre. 



Compaa Heavy Spar occurs maffive, diffeminated, reniform, 

 femi-globular ; "it has a coarfe earthy fradlure, and is feme- 

 times imperfeftly foliated ; it has a ghmmering lullre, is 

 nightly triinfluceiit, foft, and eafily frangible. It is often 

 marked with dendritic dehneations. According to Weft- 

 nnnb, it contains 



diameter ; thefe maffes have a curved lamellar 

 According to John, the conftituent parts are, 

 Sulphate of barytes, with a I 

 trace of ftrontian - j 



Sulphate of lime 

 Oxyd of lime 



Water, carbonaceous matter, 1 

 fulphur, and alumine - J 



llruai 



Sulphate of bai-ytes 

 Silex - 

 Alumine 

 Water - 

 Oxyd of iron - 



83 

 6 

 I 

 2 

 4 



96 



In DerbyHiire, this mineral is called ea-wk by the miners. 



Granular Heavy Spar occurs maffive : the flrufture is 

 finely granular ; the llruflure of the grains is lamellar. 

 This mineral nearly refcmbles granular lime-ftone, but is 

 much heavier, and does not effervefce with acids. 



Lamellar, or Cryjlalli-^ed Heavy Spar, occurs in the fol- 

 lowing fecondary forms. I . A retlangular four-fided table, 

 either perfeft, or with the terminal planes bevelled, and 

 fometimes the angles of the bevelment ai-e truncated. 

 2. An oblique four-fided table, perfect, or with the angles 

 or edges truncated. 3. A longifh fix-fidcd table, either 

 perfeiS or varioufly bevelled. 4. Eight eight -fided tables, 

 either perfect, bevelled, or truncated. Curved lamellar 

 heavy fpar occurs in diftinft concretions, which have a curved 

 lamellar ilruclure. 



Fibrous Heavy Spar has a chefnut-brown colour. It 

 occurs in reniform or botryoidal maffes, and has a plumofe 

 or diverging fibrous ftrufture. 



Radiated Heavy Spar, or Bolognefe Spar. — Its' colours 

 are, fmoke-grey, afii-grey, or yellowifh-white. It occurs 

 in roundidi comprefled pieces, which are always covered 

 ■with marie or clay. The ftrutlure is lamellar in one direc- 

 tion, and in the longitudinal frafture radiated : it is tranf- 

 lucent. It is remarkably phofphorefcent after being heated 

 and expofed when cool to the light, and carried into a 

 dark room. It was firft found at Monte Paterno, near 

 Bologna. Its conftituent parts are. 



Sulphate of barytes 



Lime - . . , 



Silex - . . 



Alumine ... 



Oxyd of iron 



Water ... 



62 



2 



i6 



14-75 

 0.25 



97 



Columnar Heavy Spar : Baryte fulphatee baccillaire, HaLiy. 

 —Its colours are, yellowifli, greyifn, and greenilh-white. It 

 occurs cryftallized in acicular oblique four-fided prifms, 

 laterally aggregated into columns ; the luftre is (hining and 

 pearly : it is tranflucent, and has a lamellar rtrufture. 



Prifmatic Heavy Spar is heavy fpar cryftallized in fonr- 

 fided or fix-fided prifms, varioufly acuminated and modified 

 by bevelments and truncations. 



Hepatite, Baryte fulphatee fetide, Haiiy, may be clafled 

 as a variety of heavy fpar, which poflefied the' property of 

 yielding a fetid fulphureous odour when lieated or rubbed. 

 It occurs in globular mafles, from an inch to a foot in 



93-58 



3-58 



0.87 



2.00 



100.03 



85.25 



According to Klaproth, 



Sulphate of barytes, with al 

 trace of ftrontian - j 



Carbon - . . 



Sulphate of lime 

 Oxyd of iron 

 Alumine ... 

 Lofs, including water and") 

 fulphur - - - j 



Hepatite occurs at Buxton, in Derby (hire. 



Heliotrope, Quarz agathe pon3ue, Hai'iy. 



Hematite, Black and Broivn ; Fer oxyde hematite, 

 Haliy. 



Hematite, Red ; Fer oligijle concretione, Haiiy. See 

 Iron-Ores. 



Hepatic Pyrites, or Lower Pyrites. See Pyrites. 



Hepatite. See Heavy Spar, Addenda. 



Highgate-Resix. See Fossil-Copal, Addenda. 



Hollow Spar. See Chiastolite, Addenda. 



Honey-Stone. See Mellite. 



Horn-stone, a mineral nearly allied in compofition to 

 flint, but has a more earthy texture ; it received its name 

 from the fuppofed refemblance to horn. A more opaque 

 variety of flint, which occurs along with flint and chalce- 

 donic flint in the fand ftrata below chalk, is called chert. ( See 

 Chf.rt, Addenda.) This is a kindof horn-ftone. Horn-ftone 

 is the petro-Jilex of fome mineralogifts, and under that name 

 is often confounded with compaB felfpar. Indurated flate, 

 which contains a large portion of filex in its compofition, 

 is fometimes called horn-jlonejlate. SaulTure, under the names 

 of pahopetre and neopetre, appears to include both the 

 fplintery horn-ftone and flinty flate of Werner. Werner 

 divides horn-ftone into three fub-fpecies, fplintery horn-ftone, 

 conchoidal horn-ftone, and wood-ftone. 



Splintery Horn-Jlone occurs of \ arious fliadcs of grey, red, 

 and green. It is generally maflive, but fometimes is found 

 in large balls, and fometimes lenticular, or in the form of 

 cryftals, in the cavities where cryftals have once occurred, 

 and hence called fuppofititious cryftals. The luftre is dull, 

 the frafture fplintery ; it is more or lefs tranflucent, is fome- 

 what lefs hard than quartz. It is infufible before the blow- 

 pipe, which diftinguidies it from compaft felfpar. The 

 latter mineral is not fo hard as horn-ftone, and has more luftre. 

 Horn-ftone paftes into compaft felfpar, quartz, common 

 jafper, and chalcedonic flint. In thefe tranfitions, it is fre- 

 quently difficult to determine among which of thefe it fliould 

 be placed. It forms the bafis of horn-ftone porphyry. 



Conchoidal Horn-Jlone is ghmmering or gliftening, with a 

 vitreous luftre ; it has a more or lefs perfeft and flat con- 

 choidal frafture. It is harder and lefs tranflucent than 

 fplintery horn-ftone. It occurs maffive, globular, and fome- 

 times forms fuppofititious cryftals. It is found in veins and 

 beds. Chert appears to belong to this fub-fpecies. 



Wood- 



