gNDGREN 
IILLEBRAND 
£* D ] MINERALS FROM OLIFTON-MORENCI, ARIZONA. 47 
134 1 ). As is common on this species, the prismatic faces arc vicinal and the s and x 
ices are striated parallel to their mutual intersection edges; hence the crystals are 
Ot suited for giving accurate measurements of the angles with the reflection goni- 
meter. One crystal was measured, and the angles of one of the rhomhohedral 
ones, given below, are sufficiently close to the calculated values to establish the 
ientity of the forms. 
Measured. Calculated. 
a x, 1120 1341 = 28° 55' 28° 48' 
s s', 0221 2021 = 83° 48 / 84° 33' 
s' a", 2021 TT20 = 48° 18' 47° 43' 
By crushing some of the material, embedded in oil under a cover glass, and exam- 
nation in convergent polarized light, occasional fragments were found which gave 
normal uniaxial interference figure, with numerous rings indicating high birefrin- 
ence. The character of the birefringence was found to be positive. Thus in all of 
ts crystallographic and optical relations the material studied is like typical dioptase 
rom other localities. 
CHRYSOCOLLA. 
This mineral (CuSi0 3 +nH 2 0) occurs very commonly in the oxidized 
>art of the deposits, but does not, except in some eases, constitute an 
mportant ore. On the whole, it is more abundant in the deposits in 
)orphyry and granite than in those contained in limestone. The usual 
)luish green or dirty green colors and conchoidal fracture characterize 
t. It occurs in seams or coatings at many of the mines — abundantly in 
he Mammoth mine on contact fissure between porphyry and limestone; 
t several prospects on the Stevens group in Chase Creek near Gar- 
eld Gulch; in the Terazas fissure vein in porphyry, near Me tea If ; at 
e Metcalf mines and many of the prospects between that place and 
orenci; at the Modoc open cut, Morenci. Technical analyses of 
rysocolla ore from Terazas mine by the Arizona Copper Company 
ve — 
Si0 2 31.(15 
CuO 34.90 
H 2 26.30 
Al 2 0, 3.80 
Undetermined 3.35 
100.00 
Normal chrysoeolla should have 34.2 per cent Si0 2 , 45.2 per cent 
JiO^ and 20.5 per cent H 2 0, but the analyses show great divergency, 
my probably being mixtures. Moreover, what has been called 
rysocolla probably includes two mineral species. 
The optical characteristics of chrysoeolla seem imperfectly known. 
Ana states that it is cryptocrystalline, while many other text-books, 
tabby one issued in 1902 by Professor Miers, call it " amorphous." 
In most cases the mineral indeed seems cryptocrystalline with bluish- 
£Jay colors of interference, but this is by no means universal, 
phrysocolla from the Modoc open cut appears as mammillary crusts 
