8 
r * 
1 
Molecular ratio 
2 
PjOi. 
39-83 
0-280 
0-280 = 1 x 0-280 
37-72 
CaO . ............. . . . . 
32-18 
0-575 
0-575 = 2 % 0-287 
31-11 
FeO 
6-86 
0-0951 
15-63 
FesOi. 
0*80 
0-005 
Ma*0*. ................ , . .... , . 
0-36 
0-005 
MnO ............. ............. 
- 0-268 = 1 x0-268 
trace 
AifO» * 
0-39 
0-004 
MgO..... ......... 
6-34 
0-159 
1-45 
F 
0-27 
0-014 
cdi ................... 
0-23 
0-006 
• 0-710 = 2* x 0-284 
HiO —105 ... .. ... 
0-15\ 
0-690 
+105. 
12-28 i 
12-15 
c .... 
0-18 
SiO*. 
0-10 
Insol. 1-40 
Less O 
Equivalent to F 
99-97 
0-11 
99-46 
99-86 
(Cr, Na, K, Sn, Ba, Ti, Cl, and WO* were absent.) 
Analysis 1. Collinsite from lake Frangois, B.C., by E, A. Thompson. 
Analysis 2. Composition of messelite is given for comparison. E. S. Dana, “System of 
Mineralogy,” p. 812. 
The formula for collinsite derived from the above ratios may be 
written P 2 0 8 Caa (Mg Fe) 2j H?0 in which the magnesium oxide is de- 
cidedly in excess of the ferrous o'xide. Thus, collinsite is a new mineral 
representing the magnesium end member of an isomorphous series of which 
messelite represents the iron end. The formula for messelite is given by 
Dana 1 as P 2 08 (CaFe)a 2| H 2 0, Since the calcium oxide content seems 
to be constant for collinsite and messelite, Dr. Wherry 2 suggests that in the 
formula the calcium should not be included with the iron and magnesium 
in a parenthesis to show isomorphism, but that the parenthesis contains 
only Mg and Fe. The G and Si0 2 are no doubt derived respectively from 
wurtzilite and andesite impurities and the F and CO 2 may be due to some 
admixed quercyite. 
Collinsite and messelite may be briefly compared as follows: 
— 
Collinsite 
Messelite 
Crystallography 
Triclinic... 
Triclinic 
+ 
Medium 
1-640 
1-653 
1-680 
0-040 
3-00 
3-3-5 
PaOsCas (Fe Mg) 2* H s O 
14-2 : 85-8 
Optically!.. 
+ 
80° 
1-632 
1-642 
1-657 
0-025 
2*95 
3-3-5 
PsOsCas (Mg Fe) 2 JHjO 
62-6 ; 37-4 
2V 
a.. 
y , . 
Birefringence .......................... 
Gravity. 
Hardness . 
Composition, .... . ...... ........... 
Ratio of MgO to FeO . . . 
iDana, EL S.: “A System of Miaeralogy," p. 812. 
*Private communication. 
