124 
CONTRIBUTIONS TO MINERALOGY. 
[BULL. 
In the following" table all available analyses of pisanite are tabu- 
lated, and one can readily see that there is no definite ratio between 
the copper and iron. The formula is then written (Ci^Fe^O^.THgO, 
pisanite being- an isomorphous mixture of melanterite and boothite. 
All the analyses are calculated to 100 per cent. a 
No. 1. 
No. 2. 
No. 3. 
No. 4. 
No. 5. 
No. G. 
CuO 
7.56 
15.85 
30. 74 
45. 85 
9.17 
16. 37 
29. 00 
45. 46 
10.07 
(16.15) 
28.84 
(44.94) 
12.61 
14. 14 
28.44 
44.81 
15. 52 
FeO 
25. 86 
28.80 
45. 34 
12.14 
SO, 
27.82 
H 2 
44. 52 
100.00 
100.00 
100. 00 
100. 00 
100. 00 
100. 00 
No. 7. 
No. 8. 
No. 9. 
No. 10. 
No. 11. 
Cuo ; 
15. 56 
10. 98 
29. 90 
43. 56 
17.45 
10.18 
28. 43 
43.94 
17.64 
9.62 
28.27 
44.47 
18.81 
8.51 
27.93 
44.75 
27.85 
FeO 
so 3 
28.02 
H 2 
44. 13 
100. 00 
100. 00 
100. 00 
100. 00 
100. 00 
5. GYROLITE. 
In the same rock and but about 50 feet distant from the place where 
the pectolite 5 and datolite occur, at Fort Point, San Francisco, Cal., 
were a number of veins of a pearly massive zeolite, which analysis 
showed to be gyrolite. The veins, ranging from microscopic size to a 
thickness of nearly a centimeter, occur in a dark basic igneous rock, 
probably a basalt. The gyrolite has replaced the rock and grown out- 
ward from both sides of the vein, forming a contact line in the middle 
where the two parts join. The mineral is grouped in spherical and 
also in massive platy or plumose aggregates. It is at times associated 
with apophyllite, but usually occurs pure. Its color on the fresh 
fracture is white, while on the weathered surface it is a brownish- 
3 r ellow. It has a decided pearly Luster and possesses a good cleavage. 
Under the microscope, a thin section of the rock containing these 
veins shows that the rock has been replaced by this secondary mineral, 
always commencing as a minute vein, probably originating in a micro- 
a A.nal. No. 1, theoretical comp. of melanterite, FeS0 4 .7Ho0. No. 2, Schaller, anal, quoted above; No. 
3, Schaller, Bull. Dept. Geol. Univ. of Cal., vol. 3, No. 7; No. 4, Hintz, Zeit. Krys., 2, 309; No. 5, Hille- 
brand, Bull. U. S. Geol. Survey No. 220, p. 105; No. 6, see No. 3; No. 7, Pisani, Comptes Rendus, 1859, 
48. 807; No. 8, see No 3; Nos. 9 and 10, Herz. Zeit. Krys., 26, 16; No. 11, theoretical comp. of boothite, 
CuS0 4 .7H 2 0. 
bEakle, A. S., Mineralogical notes: Bull. Dept. Geol. Univ. Cal., vol. 2, No. 10, 1901. 
