Mineralogy and. Geology. 131 
prismatic system, and resemble those of chrysolite. The crystals have 
pe faces of two rhombic prisms, one of 130° 36’, and the other 
1° 36’. 
Hardness = 6. Specific gravity at 18°-6 C. = 40805. 
“‘ Crystals similar to these in form, composition and mode of occur- 
rence, were described by Mitscherlich in the Annales de Chimie, t. 
XXI easurements of crystals of the same form, and a comparison 
of their angles with those of olivine, were given by one of the authors 
(W. H. M.) of the report in the third volume of the Transactions of 
e American Philosophical Society. 
“Estimating the whole of the iron as protoxyd, the composition 
would be nearly that of Fe? Si, the formula assigned by Thomson to 
the mineral from Ireland, named ‘ Anhydrous silicate of iron.’ ow, 
the slag will in constitution as well as form resemble olivine, the mag- 
hesia of the latter being replaced by protoxyd of iron. 
No. 18. No. 14. 
Composition. A sie mae — 
Analysis. Oxygen. | Analysis. Oxygen. 
Silica, . . A A 29-60. °°. «15-37 ae 12-41 
Protoxyd of iron, rage 48-43 . . 11-02 983 - . 9-07 
Sesquioxyd of iron, .  . | 17119. . 524 | 2875. . 7:28 
I rotoxyd of manganese,” . DPB. | cert ARES 617-02 acy 299 
tyra ae ee 1-28 0-59 Oo . 0-42 
egies 0-47 0-13 0-23. 0-08 
Magnesia 0-35 0-13 024 . 0-09 
| § hosphoric acid i 1/34 0-75 642 . 3-60 
‘Sulphuret of iron, 1-61 0-62 
: 10-132 102-08 
No. 14 is a slag “found by Mr. Twamley at the Bloomfield iron- 
works, Tipton, in a heap of calcined puddling furnace slag, technically 
called ‘tap cinder.’ The proprietors of these works have secured by 
nation which one of us has made (J. P.), to be sufficient to soften and 
) -) 
igglutinate the pieces of slag together, but not to effect perfect fusion. 
486 P g toge 
j 
# 
oe The. 
