GENERAL MINERALOGY OF THE DISTRICT. 
127 
Hubnerite. — 1 The only occurrence of a tungsten mineral noted in the Cripple Creek 
district is in the Puzzle vein on the level of Ophelia tunnel. Hubnerite, a tungstate of 
manganese and iron, appears here in a small vein associated with the zinc blende and 
galena and intergrown with quartz. It forms radial dark-brown to dark-green 
aggregates; the mineral is monoclinic, with excellent cleavage parallel to clinopina- 
coid; the striated prisms have partings parallel to an orthodome (102); extinctions 
are usually parallel to prisms, but occasionally oblique extinctions up to 17° are 
obtained. Its color in transmitted light ranges from almost opaque reddish brown 
to olive green, a single crystal sometimes showing several different colors. It is not 
pleochroic. The double refraction is medium strong, probably about 0.025. 
Titanite. —In microscopic, lozenge-shaped yellowish-brown crystals this mineral 
is common in many of the rocks of the district, notably in the latite-phonolite. 
Orthoclase.— Occurs as an important constituent in all of the rocks in the district, 
except the diabases and some basaltic dikes. It is also common as a mineral of the 
vein-forming period and has then the crystal form and composition of adularia. It is 
most abundant in the u granite ore” formed by partial replacement of Pikes Peak 
granite, but is also found in veins contained in breccia, latite-phonolite, or phonolite. 
In the granite it appears as crystalline coatings and as a true replacement. Where 
formed by deposition in open space it usually takes the wedge-shaped form charac¬ 
teristic of the variety of adularia called valencianite and is entirely similar to that 
mineral as described from Silver City^, Idaho.® The prevalent combination is the 
prism (110) and the unit dome (101). Between crossed nicols the crystals some¬ 
times show optical anomalies consisting in a peculiar arrangement of sectors, similar 
to the phenomena observed in certain kinds of vein quartz. 
Microcline. —Common in Pikes Peak granite. 
Albite. —Occurs as constituents of the granites and often intergrown with ortho¬ 
clase as microperthite. Not known in the district as a vein mineral. 
Oligoclase, labradorite, and anorthite. —These feldspars occur as constituents of 
many rocks of the district, but are much less abundant than orthoclase, microcline, 
and albite. Labradorite forms the principal mass of an anorthosite dike near the 
Galena mine. • 
Nepheline. —Occurs as an important constituent of the phonolite. 
Sodalite and nosean. —Occur as important constituents of phonolite and latite- 
phonolite. 
Analcite. —Occurs in phonolite, trachytic phonolite, and basaltic dikes, partly as 
an original constituent of the rocks, partly due to subsequent decomposition. 
Stilbite and natrolite. —Both these minerals occasionally form during the decom¬ 
position of phonolitic rocks. 
Tourmaline. —The only occurrence of tourmaline reported from the district 
is in a pegmatite dike said to occur near Rhyolite Mountain in granite. It contains 
large and well-developed crystals of this mineral, contained in quartz. 
Olivine. —Found as constituent of some of the basaltic dikes and the gabbros 
near Iron Mountain. 
o Twentieth Ann. Rept. U. S. Geol. Survey, pt. 3, 1900, p. 167. 
