Deposit

Long Valley Monazite Placer District

Long Valley Monazite Placer District is a deposit with published resource estimates in Idaho, recorded in the USGS USMIN rare earth element occurrence database (ver. 4.0, June 2019).

Facts on this page last re-verified Aug 12, 2026 — the oldest verification date among its current claims. How we verify.

Location: Idaho, United States (44.514, -115.990 approx.)

Commodities: rare earth elements (in monazite); ilmenite; zircon; garnet; thorium (in monazite); thorium; uranium

Published resource estimates

As compiled by USGS USMIN from the cited studies. Resource classes follow the source; "approximate" flags values USMIN reports as approximations. These are not current company reserve statements.

Material	Class	Amount	Grade	Contained	As of	Reference
thorium oxide (ThO2)	Probable Potential	215,000 t	4.35111 percent	8,230 metric tons Th	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
total rare-earth oxide (TREO)	Probable Potential	136,000 t	—	136,000 metric tons TREO	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
ilmenite (FeTiO3)	Probable Potential	2,220,000 t	—	701,000 metric tons Ti	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
total rare-earth oxide (TREO)	Unclassified	75,100 t	—	75,100 metric tons TREO	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
uranium oxide (U3O8)	Probable Potential	312.1 t	—	265.1 metric tons U	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
garnet	Unclassified	55,500 t	—	55,500 metric tons garnet	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
ilmenite (FeTiO3)	Unclassified	944,000 t	—	298,000 metric tons Ti	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
thorium oxide (ThO2)	Unclassified	120,000 t	4.31111 percent	4,530 metric tons Th	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
uranium oxide (U3O8)	Unclassified	163.1 t	—	139.1 metric tons U	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
zircon (ZrSiO4)	Unclassified	21,500 t	—	10,700 metric tons Zr	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
zircon (ZrSiO4)	Probable Potential	43,300 t	—	21,500 metric tons Zr	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
garnet	Probable Potential	132,000 t	—	132,000 metric tons garnet	Jan 1, 1980	Staatz and others (1980), Page 16 — Staatz, M.H., Hall, R.B., Macke, D.L., Armbrustmacher, T.J., and Brownfield, I.K., 1980, Thorium resources of selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.

Recorded production

Long Valley Monazite Placer District: produced approximately 9,850,000 metric tons of zircon (ZrSiO4) at 0.000118 metric tons per cubic meter, containing about 1,170 metric tons Zr, 1950–1955 (Staatz and others (1980), Page 10, Table 2)
Long Valley Monazite Placer District: produced approximately 9,850,000 metric tons of garnet at 0.004161 metric tons per cubic meter, containing about 4,090 metric tons garnet, 1950–1955 (Staatz and others (1980), Page 10, Table 2)
Long Valley Monazite Placer District: produced approximately 9,850,000 metric tons of monazite at 0.000653 metric tons per cubic meter, containing about 6,430 metric tons monazite, 1950–1955 (Staatz and others (1980), Page 10, Table 2)
Long Valley Monazite Placer District: produced approximately 9,850,000 metric tons of ilmenite (FeTiO3) at 0.002251 metric tons per cubic meter, containing about 22,100 metric tons Ti, 1950–1955 (Staatz and others (1980), Page 10, Table 2)

Record imported from USGS USMIN ver. 4.0 (June 2019). Developments after that date appear on facility records, not here; see the methodology.

Sources

U.S. Geological Survey · published Jun 1, 2019 · retrieved Aug 12, 2026 · archive unavailable: Wayback snapshot 20260427015518 of the ScienceBase item exists but the archive service returned 503 on verification 2026-08-12; recheck on a weekly pass