MINERALOGY. 



comes opaque by expofurc to the a.r. The amell^ arc 

 iomewhat elaftic ; it is foft, and adheres n.ghtly to the 

 touKue. Specific gravity 2.3. It is mfuhblc, but fo uble 

 in muriatic acid. According to Vauqueln,, the conibtuent 

 parts arc, 



Magncfia - - " 



Water 



Oxyd of iron 



Silex 



64 

 29 



2-5 

 2 



97-5 



HvcnoPHANK. See Oval, AlJ^n^a. 



Hypersten-e, Labrador HornhJench ; Diallage metal- 

 louk Haiiy. Its colours are, dark-greyilh, browniih, or 

 .rreenini-black, with generally a pfeudo-metalhc luftre, 

 feflefting a copper-red, a pinchbeck-brown, or a gold-yellow 

 lio-ht. It occurs both malTive and diffeminated ; it has a 

 lamellar ftrufture and a two-fold cleavage, the planes form- 

 ino- angles of 100" and of 80°. It is opaque, and yields a 

 greeniih-white ftreak. It is harder than common hornblende. 

 Its fpecific gravity is 3.38. Before the blow-pipe it blackens, 

 but is infufible. According to Klaproth, the conftituent parts 



are, 



Silex ... - 54.25 



Magnefia ... 14.00 



Alumine - - - 2.25 . 



Oxyd of iron - - - 24.50 



Lime - - - 1-50 



Water ... i 

 Manganefe, a trace 



97.50 



pruffian blue, but when viewed by tranfmitted light at right 

 angles to the axis of the prifm is a brownidi-yellow. Tlie 

 ftrufture is indiftinftly lamellar, with joints pafTmg through 

 the axis at right angles to the lateral faces of the prifm. The 

 frafture is uneven, pafling into conchoidal. It pafTes from 

 tranflucent to opaque. lolite fcratches quartz. Its fpecific 

 gravity is 2.5. It is not affected by acids. Before the 

 blow-pipe, it melts with difficulty into a greeni(h-grey enamel. 

 This mineral occurs at Cape de Gate, in Spain ; it is found 

 imbedded in fragments of gneifs and compaft felfpar, con- 

 tained in what is luppofed by Cordier to be a volcanic tufa, 

 which contains, befides blocks of fcoris, obfidian and bafalt. 

 lolite has alfo been found in trap at Arendal in Norway. 



Iridium, Native, has a pale ileel-grey colour ; it occurs 

 in flat fmall irregular grains in alluvial foil in South Ame- 

 rica. It has a (hining metallic luftre, a lamellar ftrufturc, 

 is brittle and harder than platina. The fpecific gravity is 

 19.5. It is proved by Dr. WoUafton to be an alloy of 

 Irrtdtum and Ofmlum ; which fee. 



Iron-Clay is of a reddifli or brownifh-red ; it occurs 

 mafiive and velicular, as the bafes of fome amygdaloids which, 

 form beds in bafaltic rocks. It is intermediate between 

 bafalt and wacke, having lefs hardnefs than the former, and 

 more than the latter. It is alfo more eafily frangible than 

 either bafalt or wacke. 



Iron-Flint is generally of a brown or brownilh-red 

 colour ; it is opaque and hard, and has an imperfeft con- 

 choidal fracture. It occurs maffive in rounded pieces, and 

 cryftallized in fmall equiangular fix-fided prifms. Its fpecific 

 gravity is from 2.5 to 2.8. It is infufible. This mineral 

 appears to be quartz rendered opaque by a chemical com- 

 bination with iron. According to Bucholz, the conilituent 

 parts are. 



Until very recently, this mineral had only been found on 

 the coaft of Labrador, where it forms a conftituent part of a 

 rock compofed of Labrador felfpar, and fometimes contain- 

 ing common hornblende and magnetic iron-itone. It has 

 been lately difcovered by Dr. MaccuUoch in fienite, at 

 Lock Scavig in Skye, alfo near Portfoy, and is fuppofed 

 to exift in many rocks which have hitherto been defignated 

 green-ftones. 



IcHTHYOPHTHALMiTE, Apoplyllte, Haliy. See Zeolite. 

 Idochase, Vefu-utaji. See Vesuvian. 

 IndIANITE, a mineral brought from the Carnatic, of 

 which we have the following account by its difcoverer the 

 count de Bournon. Its colours are white and grey, its luftre 

 (hining ; it has a lamellar rtrnfture, is tranflucent inchning 

 to tranfparent ; it fcratches glafs, but is lefs hard than fel- 

 fpar ; it occurs maflive, and is aflbciated with hornblende. 

 Its fpecific gravity is 2.74. According to Chenevix, the 

 conftituent parts are, 



Silex 



Alumine 



Lime 



Iron 



A trace of Manganefe 



42.5 

 37-5 



3 



98 



Indicolite, Indigo blue, tourmaline. See Tourma- 

 line. 



lonTi, Dichroite, occurs principally cryftaUized, in 

 fmall equiangular and equilateral fix-fided prifms, which 

 have rough furfaces. The colour is violet-blue, or dull 



99 



99-75 



Pebbles of iron-flint are ufed at Worcefter for burnifliing 

 the gilding in china. They have fometimes been found in 

 confiderable quantities in the ploughed fields near Afliby- 

 de-la-Zouch in Leicefterfliire. 



Ikon-Mica. Micaceous iron glance, or iron-ore. See 

 Iron-ores. 



Iron, Native. See Iron-ores. 



Inoia, Native and Meteoric, Fer native meteortqiie, Haiiy, 

 is the iron which has been obferved in various places to fall 

 from the atmofphere. See Stone, Meteoric, Falling 

 Stone, and Meteoric Iron, Addenda. 



Iron-Ore and Iron-Stones. (See Iron.) We fliall 

 here enumerate the diff^erent fpecies of iron-ftone, with the 

 names given to them by the French and German minc- 

 ralogifts. 



Iron Pyrites, Common ; Fer fulphure, Haiiy ; Gemelner 

 fchiuefelhles, Werner. Capillary Pyrites, Fer fulphure ca~ 

 plllalre, Haiiy ; Haarkles, Werner. Cellular Pyrites, Zell- 

 iles, Werner. Radiated Pyrites, Fer fulphure radle, Haiiy; 

 Strahliles, Werner. Hepatic, or Liver Pyrites, La pyrlte 

 hepatlque, Brochant ; Leberkles, Werner. Mag7ietlc Pyrites, 

 Fer fulphure fernfere, ou magnetlque, Haiiy ; Magnetkles, 

 Werner. Foliated Magnetic Pyrites, Blathlcher magnethiesy 

 Werner. For an account of thefe fpecies, fee Pyrites, 

 and Iron-ore. 



Ikon-Stone, Magnetic, Common, Fer oxydule, Haiiy ; 



Gfmelnsr 



