IRON. 



141 



more frequently in rocks of the coal formation, and 

 in strata of clay. Its principal localities are in 

 France, Bohemia, and Hessia. It is useful for the 

 manufacture of sulphur, sulphuric acid, and cop- 

 peras. 



10. Magnetic Iron pyrites is rarely seen in well 

 formed crystals. Count Bournon describes it as 

 occurring in irregular six-sided prisms. In general, 

 it is massive and foliated, or fine granular. Lustre, 

 metallic ; colour, intermediate between bronze-yellow 

 and copper-red ; streak, dark grayish-black ; subject 

 to tarnish ; slight action on the magnet ; brittle ; 

 hardness, considerably inferior to that of common iron 

 pyrites, or that of white iron pyrites ; specific gravity, 

 4.63. It consists of iron 62.77, and sulphur 37.23. 

 It occurs in beds, along with other minerals, usually 

 m primitive rocks. It exists plentifully at Bodenmais, 

 in Bavaria, and several districts of Stiria. In the 

 United States of America, it occurs in quartz, along 

 with blende, galena, tungsten, and along with iron 

 pyrites. Its uses are the same as have been men- 

 tioned in connexion with the other species of iron 

 pyrites. 



11. Phosphate of Iron, or P'tvianile, occurs crys- 

 tallized, in the form of a right oblique-angled prism 

 of 125 18' and 54 42', which is that of the primary 

 crystal. The crystals are long and slender for the 

 most part, though generally very small. They are 

 attached to their gangue by one of their broad lateral 

 planes, or occur in aggregated groups. Lustre, 

 pearly, approaching to metallic on certain faces ; on 

 others, vitreous ; colour, pale blackish-green ; some- 

 times approaching indigo-blue ; streak, bluish-white ; 

 the powder produced by crushing the mineral in a 

 dry state is liver-brown ; translucent, and rarely 

 transparent ; sectile ; thin laminae are flexible ; spe- 

 cific gravity, 2. 06. It also occurs massive, in small, 

 reniform and globular shapes, and imbedded nodules ; 

 also in superficial coatings of dusty particles. The 

 earthy varieties are dull, opaque, meagre to the 

 touch, and light. Their colour, on first exposure to 

 the light, is grayish, yellowish, or greenish-white, or 

 some pale tinge of blue ; but it soon passes to a dark 

 indigo-blue. In two varieties of vivianite (a friable 

 one analyzed by Klaproth, and a crystallized one from 

 Bodenmais in Bavaria, by Vogel), the following 

 chemical composition was discovered : 



Protoxide of iron, 

 Phosphoric acid, . 

 Water, . . 



47.50 

 32.00 

 20.00 



41.00 

 26.40 

 31.00 



It decrepitates before the blowpipe, but melts, if 

 first reduced to powder, into a dark-brown or black 

 scoria, which moves the magnetic needle. It is solu- 

 ble in dilute sulphuric and nitric acids. It occurs 

 in a variety of geological situations. The crystals 

 are found in copper and tin veins, and sometimes in 

 greywacke accompanying native gold ; also in basalt 

 and trap rocks. The earthy and n:assive varieties 

 are imbedded in clay, and often accompany bog iron 

 ore. The crystalline varieties come from Cornwall 

 and Bavaria ; the foliated and earthy varieties abound 

 (especially the former) in the United States of Amer- 

 ica. It is confined to argillaceous and ferruginous 

 deposits, and is sometimes found in connexion with 

 bones, and very usually filling up the casts of belem- 

 nites and other fossils. The earthy vivianite is some- 

 times employed as a pigment. 



12. Arseniate of iron occurs in small cubic crystals, 

 which are either unmodified, or have their alternate 

 angles or their edges truncated. Lustre, adamantine, 

 not very distinct ; colour, olive-green, passing into 

 yellowish-brown, bordering sometimes upon hyacinth- 

 red and blackish-brown, also into grass-green and 

 emerald-green ; streak, similar to the colours ; trans- 

 lucent on the edges ; rather sectile ; scratched by 



fluor ; specific gravity, 3.00. According to two ana- 

 lyses, it consists of 



Oxide of iron, . . 

 Arsenic, ... 

 Oiide of copoer, 



Silica, 



Carbonate of lime. 

 Water . . 



45.50 



31 00 



9.00 



4.00 



0.00 



lo.ao 



48-00 

 18.00 

 0.00 

 00 

 2.00 

 3200 



Exposed to a gentle heat, its colour is changed into 

 red. In a higher degree of temperature, it intu- 

 mesces, gives little or no arsenic, and leaves a red 

 powder. Upon charcoal, it emits copious fumes of 

 arsenic, and melts in the inner flame, into a metallic 

 scoria, which acts upon the magnetic needle. It 

 principally occurs in veins of copper ores, traversing 

 the older rocks, and its chief localities are Cornwall 

 and Saxony. 



13. Carbonate of Iron, or Spathic Iron Ore, occurs 

 crystalline and massive. Its crystals are acute rhom- 

 boids, sometimes perfect, or only having the terminal 

 angles replaced, six-sided prisms, and lenticular 

 crystals. They are very easily cleavable, yielding 

 obtuse rhomboids of 107 and 73. Lustre, vitreous, 

 inclining to pearly ; colour, various shades of yellow- 

 ish-gray, passing into ash and greenish-gray, also into 

 several kinds of yellow, white and red ; streak, white; 

 translucent in different degrees ; brittle ; hardness, 

 nearly identical with that of fluor ; specific gravity, 

 3.829. It occurs massive, in broad, foliated and 

 granular masses ; also in fibrous botryoidal shapes, 

 whence it has received the name of spherosiderite. 

 Two varieties of this species, 1. the spherosiderite, 

 and 2. a cleavable variety from Newdorf in the Hartz, 

 have yielded to Klaproth, (1.) (2.) 



Protoxide of iron, 

 Carbonic acid, 

 Oxide of manganese, 

 Lime, 



63.75 

 34.00 

 0.75 

 0.00 



47.50 



36.00 



3.30 



1.25 



Magnesia, . 0.52 



Before the blowpipe, it becomes black, and acts upon 

 the magnetic needle, but does not melt. It colours 

 glass of borax green. It is soluble with difficulty in 

 nitric acid, particularly if not reduced to powder. 

 On being exposed to the air, it is gradually decom- 

 posed : first the colour of the surface becomes brown 

 or black ; afterwards, also, the streak is changed 

 into red or brown ; hardness and specific gravity are 

 diminished ; and even the chemical constitution is 

 altered, the whole being converted into hydrate of 

 iron. It frequently occurs, along with carbonate of 

 lime, in veins and beds, in primitive rocks ; also in 

 metalliferous veins, accompanied by galena, gray 

 copper ore, and iron and copper pyrites. Immense 

 beds of it exist in Stiria and Carinthia, as well as in 

 France, Switzerland, and Siberia. In the UnitedStates 

 of America, there is a vein of it at New Milford in 

 Connecticut, crossing, with the breadth of six feet, 

 an entire mountain. In France, Stiria, and Carinthia, 

 large quantities of cast and wrought iron are obtained 

 from the sparry iron ore, but particularly steel, for 

 the production of which it is highly valuable. 



14. Oxalate of Iron, or Humboldtine is an ore of 

 iron found near Berlin, in Bohemia, in a moor-coal, 

 or friable lignite. It consists of protoxide of iron 

 53.56, and oxalic acid 46.14. It is supposed to owe 

 its origin to the decomposition of succulent plants. 

 It occurs in small flattish masses, of a light yellow 

 colour ; is soft, yielding to the nail, and of the specific 

 gravity of 1.3. By rubbing, it acquires resinous 

 electricity. It decomposes easily on live coals, giv- 

 ing out a vegetable odour. It is insoluble in boiling 

 water and alcohol. 



15. Sulphate of Iron or Copperas. This salt is 

 not frequently found in nature, in distinct crystals, 

 but usually occurs in stalactitic, botryoidal and 

 reniform masses, and occasionally pulverulent. The 



