The U.S. Bureau of Mines and the U.S. Geological Survey identified many areas of the John Muir Wilderness as having

marginal and subeconomic resources of tungsten, molybdenum, copper, gold, and silver.  Geologic, geochemical, and geophysical

evidence suggests that undiscovered deposits may also exist within the wilderness.  Tungsten is the principal metallic commodity

in the area, and with accompanying resources of gold, copper, silver, and molybdenum, is found along conflicts between granitic

rocks and metamorphosed calcareous sedimentary rocks in the Pine Creek and Mount Morrison roof pendants and in many smaller

septa located elsewhere.  Gold and silver resources in the wilderness are present around Kearsarge Peak, 2 miles northeast of

Kearsarge Pass, and along Hilton Creek; marginal resources of silver, copper, lead, and zinc exist along Hilton Creek.  A small

subeconomic resource of uranium may exist near the northwest boundary of the wilderness.  Small cobalt resources occur near the

head of Bishop Creek.  Stone, sand, and gravel are abundant, but such material is available closer to markets.  This study revealed no known potential for coal, oil, gas, or geothermal resources.  The north boundary of the wilderness adjoins the south edge of the

Mono-Long Valley "Known Geothermal Resource Area" (KGRA); however, the greatest geothermal potential is associated with

Quaternary volcanic rocks which do not extend into the study area.  A single hot spring exists within the wilderness, but the rock

type indicates a local source not associated with the KGRA heat source.  Along the west side of the Pine Creek pendant, adjacent

to the wilderness, are tactite zones forming the largest, most productive tungsten reserves in the United States. 

NICOLE HILTON CREEK MINE

    The Nicoll Hilton Creek mine, owned by D.H. Nicoll of Bishop, Calif., is located at the east base of Nevahbe Ridge in the canyon of Hilton Creek.  The workings are at an altitude of 9,700 to 9,850 feet and can be reached by a private road from U.S. Highway 395.  The mine is snowbound for 4 to 6 months of the year, but the property could be kept open through the winter, although this has not been done in the past.  The deposit was first exploited sometime after 1940, and the total production to the end of 1954 was about 7,000 tons of ore containing about 1 percent of W03, according to R. B. Schwerin, the present operator (1955).

    The workings consist of a crosscut driven about 200 feet on a general westward heading, an opencut about 100 by 60 feet with a small underground room at one end, and a raise from the crosscut to the floor of the pit (pl. 5).  Since the mine was mapped in August 1954, the adit has been extended a short distance northward along the contact between the quartz monzonite and the tactite.  About 1,000 feet south of the adit, exposures of scheelite-bearing tactite have been prospected at the surface.

    The deposit is localized in a re-entrant along the northward-trending contact between the Wheeler Crest quartz monzonite and the Hilton Creek marble.  In the mine area the metamorphic rocks project eastward into the quartz monzonite, so that in plan view the ore body is surrounded on three sides by the intrusive rock.  Also, the strike of the marble, which is generally concordant with the northward-trending contact, bends in toward the re-entrant and is markedly discordant.  The easternmost end of the marble salient is almost wholly converted to tactite.  The relationships suggest that the peculiar configuration of the contact has been a contributing factor in the localization of the ore.  The large mass of diorite that occupies the part of the re-entrant in the granitic contact along with the tactite is probably the result of contamination of the granitic rock by metamorphic material.

    The tactite consist chiefly of red-brown grossularite-andradite garnet (Gr60-70) and green diopside-hedenbergite pyroxene (Di40-55), with lesser amounts of dark-green hornblende, quartz, and calcite.  Small crystals of scheelite, ranging in size from pin points to 2 or 3 mm in diameter, are disseminated through the tactite.  Some of the scheelite occurs in “streaks” formed by tabular concentrations of tiny scheelite crystals.  In most specimens the streaks are parallel to indistinct mineral layers that may reflect original bedding.  The ore also contains small amounts of molybdenite and its alteration product, powellite.

PHELPS HILTON CREEK MINE

    The Phelps Hilton Creek mine, owned by R. W. Phelps of Bishop, Calif., is about 2,500 south of the Nicoll Hilton Creek mine along the same quartz monzonite contact.  The workings range in altitude from 9,900 to 10,000 feet.  The mine is accessible from U.S. Highway 395 by means of a private road, 5 miles long, that was built in 1939.  In the fall of 1939 and the summer of 1940, the Bishop Tungsten Co., as lessee, shipped 553 tons of ore from which about 350 unites of WO3, were recovered.  Production from 1941 to the end of 1955 totaled about 6,000 tons of ore averaging about 0.6 percent WO3, (3,600 units), according to G. B. Hartley, the present lessee (1955).  The workings consist of two opencuts – one about 180 by 15 to 30 feet and another about 90 by 50 feet, a winze, and a 65-foot crosscut from which a raise to the surface was driven (pl. 6).

    Scheelite-bearing tactite occurs in two bodies along a segment of the contact between the Wheeler Crest quartz monzonite and marble interbeds of the siliceious hornfels unit that overlies the Hilton Creek marble farther north.  The contact in general strikes N. 20 degrees W. and is nearly vertical.  The beds are concordant in strike but dip gently to steeply westward away from the contact.  The ore body is localized in a large re-entrant in the quartz monzonite contact (pl. 1), similar in some respects to the ore body at the Nicoll mine but showing concordant rather than discordant relations.  The concordancy is reflected in the formation of tactite parallel to the granitic contact in contrast to the discordant relations of the tactite at the Nicoll mine.

    Most of the production has come from the southern-most tactite body, which measures 135 by 25 feet in the plan and is developed by means of the elongate opencut.  Although the tactite body generally parallels bedding in the marble, its shape is irregular in detail, as shown the the unreplaced marble remnants along the west side of the opencutand by reconstruction of the original outcrop (pl. 6, section A-A’) based on information supplied by G. B. Hartley and L. A. Wright (written communication, 1954).  The tactite is similar in composition to that at the Nicoll mine, except that it contains more quartz, particularly along the quartz monzonite contact.  The scheelite is typically fine grained, but no information is available concerning its distribution within the tactite.  The ore contatins small amounts of molybdenite locally.

FILIPELLI PROSPECT