J. B. Pearse on Minerals of the Chlorite Group. 223 
of chrome, and one and a third per cent less of protoxyd of 
iron in the red than in the green, the first question as to the 
cause of the difference of color is unanswered by analysis. It 
is possibly due to molecular arrangement. 
The following formule exhibit the number of each class of in- 
gredients, the sesquioxyds of chrome, iron, and aluminum being 
represented by Al,O, and the protoxyds of magnesium, calcium, 
Iron, and nickel, by Mg,O, because aluminum and magnesium 
constitute by far the larger proportion of the bases. 
Green, 5Si0,+2Al,0,+9Mg,0+8H,0. 
Red, &.,  7Si0,+2A1,0,+13Mg,0+10H,0. 
Without attempting at present to reconcile these numbers to 
any theory of the silicates, it will prove interesting to discuss 
the reliable results of analysis attained by different chemists, with 
different specimens of this and other minerals referable to the 
chlorite group. In order to show their mutual relations more 
clearly, [ subjoin a table of their atomic composition, reducing 
them all to the proportions arising from two atoms of alumina. 
* Proportion of atoms in chloritic minerals. 
SiO, Al,O,; Mg,O0 H.O Analyst. 
1, Kammererite, erystallized, 5 2 8 8 ermann, 
2. My green, rs 5 2 9 8 Pear 
3, Chlorite (average analysis) 6 2 10 8 Rammelsberg 
4. Kammererite, fibrous, 6 2 10 8 Hermann 
5. Chonikrite, massive, ae 10 6 von Kobell 
6. Rhodophyllite, crystallized, 7 2 12 10 Genth. 
7. My red, e 7 2 19° 10 Pearse, 
8. Kammererite, « 8 2 14 10 Smith & Brush. 
9. Pyrosclerite, 8 2 12 10 von Kobell. 
10. Tabergite, 9 2 14 10 Svanberg. 
11. Kammererite, crystalline, 9 2 11 10 Hartwall, Garrett. 
12, Pyrosclerite, impure, 9 2 14 6 Lychnell. 
ssion. 
Genth’s analysis of rhodophyllite (6) gives nine or ten sae 
of water, and twelve atoms of magnesia; my red, and reddish- 
green (7) give ten atoms of water and rather less than thiniees 
atoms magnesia. I therefore prefer the formula I have given 4 
Genth’s rhodophyllite, with which my red is identical. Smit 
& Brush’s kiimmererite differs from rhodophyllite by an atom 
of olivine. These two formule may be regarded as reliable, be- 
ing derived from well executed analyses of crystallized specimens. 
