ZEOLITE 



the pofiibility of cryftalline arrangements taking place under 

 cotnprefTion in fubftancea that would be diffipated by heat 

 under the common preifure of the atmofphere. It is pro- 

 bable, however, that many zeolitic fubftancea which occur 

 in bafalt or lava have been infiltrated into the cavities at a 

 later period, and are even forming at the prefent day in 

 ancient lavas and bafalts. 



Some of the minerals claffed with the zeolite family have 

 ' been defcribcd in our preceding volumes. See Apophy- 



LITB, or ICTIIYOPTHALMITE. 



Malc'ime, or Cubinte, formerly called by Werner cubic 

 zeolitt, is generally white, fometimes reddifh-whitc, or red. 

 It occurs fometimes maffive, but more generally cryftaUized 

 in perfedl cubes, or with the angles more or lefs deeply 

 acuminated, or in twenty-four-fided cryftals, like thofe of 

 the leucite, having each of the fides equal and fimilar tra- 

 peziums. The ftrufture prefents flight indications of clea- 

 vage, parallel with the fides of a cube. The frafture is com- 

 paA and flatly conchoidal, paffing into fine-grained, uneven. 

 It is tranflucent, femi-tranfparent, or tranfparent, and has 

 a ftiining luftre, between vitreous and pearly. It is fufS- 

 cicntly hard to fcratch glafs, but is eafily frangible. The 

 fpecific gravity of cubicite is 2.44. It becomes eleftric 

 by rubbing. Before the blow-pipe it melts into a tranf- 

 parent glafs. According to Vauquelin, the coQJlituent 

 parts of this mineral are. 



Silex 



Alumine 



Lime 



Soda 



W^ter 



58 



18 



2 



JO 



8-5 

 96.5 



This mineral occurs moft frequently in cavities in rocks 

 of the trap formation, accompanied with zeolite ; but it is 

 fometimes found in metallic veins in fchiftofe rocks, accom- 

 panied with various ores, and with calcareous fpar and 

 quartz. The name analclme was given to it by Haiiy, fig- 

 nifying a body with little power, on account of the feeble 

 eleflricity excited in it by friftion. 



Chabafut, Chabafie, Haiiy, is nearly allied to cubicite, 

 and was formerly claffed with it. The cryftallization is 

 different ; the form is not perfeftly cubical, but flightly 

 rhomboidal, the angles of the rhomboid being 94° and 86°, 

 either perfefl, or with the obtufe lateral edges truncated, 

 and fometimes both the fix obtufe lateral edges and fix 

 obtufe angles are truncated. The cryftals are tranfparent 

 or tranflucent. The luftre is vitreous, and externally fplen- 

 dent, internally gliftening ; the frafture is imperfeftly con- 

 choidal, or fine-grained, uneven. It fcratches glafs a little. 

 The fpecific gravity of this mineral is 2.7. It is fufible 

 into a white fpongy enamel. According to Vauquelin, 

 the conftituent parts are, 



Silex 



Alumine - 



Lime 



Soda with potafh 



Water 



43-33 

 22.66 



99.67 



The fituation in which this mineral occurs is nearly the 

 fame with that of analcime. The name was given it by 

 Haiiy, from chabazion, an unknown ftone mentioned in the 

 poems of Orpheus. 



Laumoniu, Ziolithe efflonfcente, Haiiy. — Its colours are, 

 yellowifti-white, fnovc-white, and greyifli-white. It occuri 

 maffive and cryftaUized in oftahedral prifms, with edges 

 apparently rounded ; the fummits of the cryftals are di- 

 hedral. The cryftals are fmall, lining drufy cavities. 

 The ftrufture is lamellar, and has a two-fold cleavage : it 

 is tranfparent or tranflucent when frefh ; but on expofure to 

 the atmofphere foon becomes opaque, lofiiig its hardnefs, 

 and yielding to the prefTure of the finger. When frefh it 

 fcratches glafs. The fpecific gravity is 2.23. Bournon. 

 It forms a jelly with acids. Before the blow-pipe it intu- 

 mefces, and is changed into a white enamel. According 

 to Vogcl, the conftituent parts are, 



Silex 



Alumine ... 



Lime ... 



Water ... 



Carbonic ... 



This mineral, which agrees in its principal charafters 

 with zeolite, was firft found in Brittany, by M. Gillet 

 Laumont, after whom it has been named by Werner. It 

 has been found alfo at Paifley, in Renfrewfliire, in amyg- 

 daloid, accompanying cubicite. Laumonite difintegrates 

 fo rapidly, that for its prefervation it requires to be kept in 

 well-clofed bottles. 



Crofs-Slone, Harmotome, Haiiy, occurs in fmall cryftals : 

 the form is generally a broad reftangular prifm, terminated on 

 each extremity by four rhombic faces, with their acute 

 angles fet in the lateral edges of the prifm. Sometimes the 

 edges of tlie rhombic faces are bevelled in one direftion. 

 But the name crofs-ftone is derived from the frequent oc- 

 currence of two prifms interfefting each other, having one 

 common axis. The broader planes by this interfe<5lion 

 projeft, and form the figure of a crofs when the prifm is 

 viewed at the end, or in the direftion of the axis. Tlie 

 colour of crofs-ftone is generally a greyifh-white, which 

 pafFes into fmoke-grey : it is fometimes a yellowifli-white, 

 pafling into cream-yellow, and red. It is tranflucent or 

 tranfparent, with a luftre between vitreous and pearlv. 

 The fradlure is uneven, or imperfeftly conchoidal. It is 

 fuppofed, by profefTor Jamefon, to have an imperfeftly 

 foliated ftrufture. It fcratches glafs feebly. The fpecific 

 gravity is 2.33. Before the blow-pipe it emits a yellowifh 

 phofphoric light, and melts with intumefcence into a colour- 

 lefs glafs. It docs not gelatinize with acids. This mineral 

 differs from other members of the zeoHte family, by con- 

 taining barytes as an ingredient in its compofition. Accord- 

 ing to Klaproth, its conftituent parts are, 



Silex .... 



Alumine 

 Barytes 

 Water - 



49 

 16 



»5 



98 



Dipyre, Haiiy ; SchmelzJIein, Werner. — Its colours are, 

 light pearl-grey, greyifh-white, or reddifh-white. It occurs 

 maffive and cryftaUized, in aggregated, flender, oftahedral, 

 acicular prifms. The ftrufture is lamellar, with joints 

 parallel to the fides, and to the diagonal of a reftangular 

 prifm. The luftre is intermediate, between vitreous and 

 pearly : it is tranflucent. This mmeral is fufBciently hard 

 to fcratch glafs ; but is very frangible. The fpecific gra- 

 vity 



