Inventory of Significant Mineral Deposit Occurrences in the Headwaters Project Area in Idaho, Western Montana, and Extreme Eastern Oregon and Washington

The significant mineral deposit inventory supports the U.S. Geological Survey
Headwaters project, which will provide Federal land management agencies with
basic geologic and mineral resource information that can be used to manage
near-term mineral resource development activity. The Headwaters study is
focused on areas in Idaho lying north of the Snake River plain and in western
Montana where a preponderance of the lands are managed by the U.S. Forest
Service. The scope of this mineral resource inventory embraces a broader
geographic area that includes all of Idaho, the western half of Montana and
small portions of extreme eastern Oregon and Washington.

This inventory covers only significant mineral deposits. Significant deposits
are those deposits where a mineral or natural material endowment occurs in such
a high concentration that it is reasonable to expect that recovery was or
could, in the future, be economically viable. Minimum endowments proposed by
Long (personal communication) for 46 commodities have been used in this
compilation. For deposits of other commodities where minimum endowments have
not been established a default deposit size minimum of one million metric tons
of ore has been utilized. A significant status has also been applied to
deposits where a commodity or material is of a highly unusual nature.

Data collection was limited to deposit attributes that reflect directly on the
endowed size and location of a deposit, and ancillary information that can be
used in assessing regional mineral resource potential. The data are organized
in topical information categories that include name, location, deposit
classification, discovery date, production and resources, surface area,
development status, and source of new information. Data were extracted from a
diverse array of sources that includes scientific, technical, and trade
publications of public and private institutions, organizations, and
associations that follow and report on scientific, business, and environmental
issues in the minerals industry; company financial reports, news releases, and
technical reports available at company web sites; mineral information databases
maintained by Federal and state agencies involved with monitoring and
regulating mining activities and compiling mining industry statistics; and oral
communications with individual mining company personnel and with staff of
Federal and state regulatory agencies. Several formatting conventions are used
to indicate what the relative accuracy of the numerical data is believed to be.

A total of 256 significant deposit sites are identified by location and
deposit-type. Production and resource figures are given in both English and
metric units and the approximate surface areas associated with three aspects of
deposit development are expressed in acres. Of the 256 sites, 208 have some
history of past or present production, of which 23 are currently producing and
mining could resume at 7 others on short notice with a rise in commodity
prices. Within the 208 sites are 34 placer districts and two zeolite operations
wherein mining activity on a small scale occurs intermittently. There are 166
sites where the presence of a significant resource has been recognized, of
which 49 have no prior history of development. Due to the presence of a
significant resource, these 166 sites are candidates for consideration when
addressing issues associated with management of near-term mineral development.

[Summary provided by the USGS.]