812 The American Naturalist. [October, 
% FeC 2 V (over œ) B 
Fayalite Rockport, 68.1 49° 50 1.864 
Hortonolite Monroe, 47.3 69° 24’ 1.791 
Chrysolite, Auvergne, 13.0 89° 36’ 1.692 
Chrysolite, Vesuvius, 12.6 89° 42’ 
Chrysolite, Hawaii, 10.3 wi 
Chrysolite, Egypt, 9.2 91° 19 1.678 
Chrysolite, N. M., 8.6 91° 24’ 
Chrysolite, Unknown, ? 92° 14’ 1.678 
Chrysolite, East Indies, l 92° 45’ 1.670 
. Forsterite, Vesuvius, 2 (2) 93° 50’ 1.657 
At about 12% FeO, therefore, the optical character changes from 
positive to negative. 
Rhodophosphite and Tetragophosphite.—The rare mineral 
locality at Horrsjéberg in Wermland, Sweden, is the source of these 
two new minerals recently described by Igelström. The rhodophos- 
phite occurs in large quantities in layers reaching a thickness of 2% 
feet, so that it can be mined profitably. At one locality it is found in 
the form of hexagonal prisms. From the partial analysis, it appears 
to be chiefly a calcium phosphate, with considerable quantities of fer- 
rous iron and manganese, also chlorine, fluorine, and sulphuric acid. 
The formula proposed is 20 (RO), P,O, + 4 (Ca Cl,, CaF,) + Ca SO,, 
where R= Ca, Mn, Fe, or Mg. The mineral is allied to svanbergite. 
Tetragophouphius oceurs in “ four-sided ” plates, or as a coating on 
he containing cyanite-damourite rock. The two an- 
alyses are: 
PO; : 36.92 33.64 
Al,O, 40.00 41.81 
FeO, MnO 951 9.51 
MgO, CaO 7.50 6.74 
H,O 5.96 8.30 
These lead to the formula (Fe, Mn, Mg, Ca), P,O, + (AI,O,), 
P,O, + 3H,0. It is somewhat lighter blue than lazulite, which it 
seems here to replace. The . Gusblatt-phosphat ” (light blue phos- 
phate) from the Westana Mts., Prov. Skane, Sweden, analyzed by 
Blomstrand in 1868 seems to be undoubtedly the same mineral. He 
assigned the formula (Ca, Mg), P,O, + (AI,0,), P,O, + 3H,0. 
6 Zeitschr. f. Kryst., XXV, pp. 433-436, 1895. 
