hansome.] GANGUE MINERALS. 75 
constituent in some of the rich Camp Bird ore. It probably occurs 
also in visible masses in portions of the latter lode, although none was 
seen at the time of visiting the mine. It is abundant in the Morning 
vein of the Japan mine, and in the Empire- Victoria vein with hiib- 
nerite. This latter association, however, is much more strikingly 
shown on the Adams claim, near Gladstone, as described on page 256. 
On the whole, however, it is not a common gangue mineral in this 
quadrangle, and when not too abundant is frequently associated with 
free gold. 
Rhodonite. — MnSi0 3 . Triclinic. Occurs only in cryptocrystalline 
massive form in Silverton quadrangle. Color, rose pink, fading and 
then turning black on exposure to the weather. Hardness, 5.5-0.5. 
Specific gravity, 3.5. 
The silicate of manganese, comprising much of the so-called "pink 
spar" of the miners, occurs in many of the larger lodes of the north- 
east quarter of the quadrangle as a fine-grained pink material, very 
hard and tough, forming partitions between the ore-bearing portions 
of the lodes, as elsewhere described. It is a conspicuous and abun- 
dant constituent in tli*' Sunnyside lode, in the neighboring lodes in 
Placer Gulch, and on Treasure .Mountain, particularly in the domi- 
nant northeast fissures, and occurs much less abundantly in other 
lodes of the northeast quadrant. It is also found in the Saratoga 
mine, near [ronton, where ii has partly replaced limestone. It is 
often difficult to distinguish this mineral by inspection and ordinary 
physical tests from the pink carbonate of manganese, rhodochrosite, 
when both are massive. This is due to the fact that the rhodonite is 
seldom pure, but is associated with quartz, calcite, and rhodochrosite 
in grains or crystals of microscopic dimensions. The massive rhodon- 
ite, when powdered, often effervesces slightly with acids, due to this 
slight admixture of carbonates. The greater part of the pink powder 
remains insoluble in dilute, boiling hydrochloric acid, and this fact 
and an examination of thin sections under the microscope show that 
the so-called k> pink spar" of the Sunnyside and neighboring mines is 
the manganese silicate, rhodonite. 
Zunyite. — A very basic orthosilicate of aluminum. (Al(OH,F, 
Cl) 2 ) 6 Al 2 Si 3 12 . Isometric, tetrahedral. Colorless. Hardness, 7. Spe- 
cific gravity, 2.8. 
This mineral, which was first described and named by Hillebrand, 1 
from th< i Zuni mine, is limited in its occurrence, so far as known, to 
the Zuni and to one or two adjacent prospects on Anvil Mountain. 
It occurs as small tetrahedral crystals up bo 5 millimeters (three- 
sixteenths of an inch) in diameter, embedded in guitermanite or its 
oxidation product^ lead sulphate, and associated with pyrite, enar- 
gite, bournonite, kaolin, and barite. The chemical composition of 
*On zunyite and guitermanite, two new minerals from Colorado: Proc. Colo. Sci. Soc., Vol. I, 
1881, pp. 124-129. Also Bull. U. S. Geol. Survey No. 20, 1885. 
