168 H^MACHATES. 



of Quartz presenting incisions, as if pro- 

 duced by hacking it in various directions 

 with a knife or other sharp instrument. 

 These indentations are occasioned by laminte 

 or laminar crystals of other minerals once 

 imbedded in the Quartz, the casts of which 

 only are now left, the included minerals 

 themselves having decomposed or been 

 otherwise removed. 



HiEiMACHATES (from MfjM, blood, and 

 "Axoi-Tvi;, agate), the name given by the 

 ancient Greeks to Agate sprinkled" with 

 spots of red Jasper. 



HAEMATITE. See Hematite. 



Hafnefjokdite. A variety of Oligo- 

 clase from Hafnefjord, in Iceland. 



Analysis, bv Forchhammer : 

 Silica ." . . . . 61-22 



Alumina 

 Peroxide of iron 

 Lime . 

 Magnesia 

 Soda 

 Potash . 



23-32 



2-40 

 8-82 

 0-36 

 2-66 

 trace 



98-68 

 Haidingerite, Berthier. See Berthie - 



RITE. 



Haidingerite, Turner, Rhombic: pri- 

 mary form a rectangular four-sided prism. 

 Usually occurs in minute crystals aggre- 

 gated into botryoidal forms and drusy 

 crusts. Colour and streak Avhite, with a 

 vitreous lustre. Transparent to transkicent. 

 Sectile. Slightly flexible in thin laminas. 

 H. 1-5 to 2 5. S.G. 2-848. 



Fig. 225 



Comp. Di-arseniate of lime or Ca^ As + 



3H = lime 28-28, arsenic acid 58-08, water 



13-04 = 100. 



Analysis, by Turner : 



Arseniate of lime . . 85-68 

 Water 14-32 



100-00 

 Dissolves readily in nitric acid. 

 BB it is almost entirely volatilized with 

 a dense white arsenical vapour. 

 , Locality. Joachimsthal, where it occurs 

 associated with Pharmacolite, from which it 

 may be distinguished by its form and lustre ; 

 and by containing only half the quantity of 

 water. 



HALLOYLITE. 



Name. After Herr W. Haidiuger of 

 Vienna, by Avhom it was first noticed. It 

 is a very rare mineral. 



Hair Pyrites, Jameson. See Mille- 



RITE. 



Hair Salt, Jameson. Magnesia Alum. 

 See Alunogen. 



. Comp. Tersulphate of alumina, or Al 



S3 + 18H. 

 Analysis, from Bilin, by Rammelsherg : 

 Silica . . ... . 35-31 



Alumina .... 15-86 



Water 48 88 



100-00 



Brit. Mus., Case 55. 



Hair Stone. Rock Crystal inclosing 

 capillary crystals of Rutile, crossing each 

 other and traversing it in various directions. 



Halbazurblei, Rammelsherg, See Cale- 



DONITE. 



Halbopal. See Semiopal. 



Hallite. a variety of Websterite found 

 with Gypsum, in Plastic Clay, at Halle in 

 Prussia. 



Comp. A1S + 9H. 





Analysis, by Stromeyer : 

 Alumina 

 Sulphuric acid 

 Water .... 



. 20-26 

 . 23-36 

 . 46-38 



100-00 

 Halloylite ; Halloysite, Berthier. 

 Halloyte. a siliciferous hydrate of alu- 

 mina or Kaolin, occurring in soft, smooth, 

 compact amorphous masses, having the ap- 

 pearance of Steatite. Colour white, gene- 

 rally with a slight tint of blue, and a waxy 

 lustre. Translucent at the edges or becomes 

 so in water, which it imbibes, giving off 

 numerous globules of air. Adheres to the 

 tongue. Yields to the nail, and affords a 

 shining streak. Fracture conchoidal, like 

 that of wax. S.G. 1-8 to 2 1. 



Cornp. Al Si + 3H. 



Analysis, from Housscha, by Berthier : 



Silica 47-75 



Alumina .... 35-49 

 Water 16-76 



100-00 

 Loses weight when exposed to a high 

 temperature, and becomes much harder, and 

 of a milk-white coJoui-. 



Decomposed by sulphuric acid, with sepa- 

 ration of gelatinous silica. 



