G. J. Brush on native hydrates of Iron. 221 
localities it would appear that the mineral is of common occur: 
rence. It has heretofore been confounded by most mineralo- 
gists with hematite which it so strongly resembles in physical 
characters. It may be readily distinguished from hematite by 
simply heating a fragment in the closed tube, when it decrepi- 
tates violently and gives off a large amount of water. 
ermann does not give the pyrognostic characters of turgite, 
but Breithaupt in his description of hydro-hematite makes par- 
ticular mention of its, characteristic decrepitation when heated. 
The turgite is described by Hermann as being associated with 
tied ores; its chemical composition is however identical with 
hydrohematite, and as it has priority of publication the species 
must bear the name of turgite, and hydrohematite be inlay 
aS & synonym. 
We have therefore three well defined hydrates of iron occur- 
Turgite, Fe+ 34H 
Gothite, » Fe+ H 
Limonite, #e + 13H 
. Two other hydrates have been described containing respect- 
\vely two and three atoms of water. Murray* found in a brown 
Ton ore from Hiittenrode in the Hartz— 
Fe 81-41, 1117-96, Si0-17, Carbon 0:-46=100, giving the formula #e-4-2H1. 
A compound of similar composition from Kilbride in Ireland, 
having a pitchy color, analyzed by Haughton, gave— 
Fet715 W043 Sios0 Me. #6 1-60—99-48 
_ Xanthosiderite also appears to be a mineral of like composi- 
Hon, but its mixture with a silicate of unknown composition 
Tenders it difficult to conclude positively that it belongs here. — 
- H. Churcht has analyzed a stalactite of a rust-colored ferric 
hydrate from Botallack mine in Cornwall, which gave— 
#e 78-78, H24-40, loss, ®, and organic matter 1°76 = 100, giving the formula 
Pe + 3H = Fe 74-77, H 25°83. 
Other analyses of ferric hydrates by many different analysts, and 
™ a great range of localities, give an amount of water which 
Sorrespond to one or the other of these last two hydrates; but as 
--©S contain also either organic matter, phosphoric acid, or silica 
in the combined state, it is impossible, without further investiga- 
Hon, to know to what hydrate to refer them. : a 
The artificial ferric ydrate precipitated by ammonia from 
ferric chlorid varies in composition according to the method of 
* Rammelsberg Mineralchemie, 150, + Journ. Chem. Society, Il, iii, 214. 
