Deposit
Round Top
Round Top is a deposit with published resource estimates in Texas, recorded in the USGS USMIN rare earth element occurrence database (ver. 4.0, June 2019) and the USGS USMIN gallium deposits database (ver. 1.0, 2021).
Location: Texas, United States
Commodities: rare earth elements; beryllium; niobium; hafnium; tantalum; tin; uranium; thorium; aluminum; gallium; iron; lithium; magnesium; manganese; potassium; rare-earth elements; scandium; sodium; yttrium; zirconium
Deposit model: peralkaline intrusion · unclassified · Peralkaline intrusion-related REE deposits · Unclassified
Tracked facility at this deposit: USA Rare Earth Round Top Mountain
Geology
“The Round Top rhyolite was divided into five different alteration phases based on the intensity of hematitic and hydrothermal alteration: gray rhyolite, pink rhyolite, red rhyolite tan rhyolite and brown rhyolite in the order of least to most altered. Hematitic alteration is a replacement of the magnetite by hematite and gives the rhyolite a red to pink color. Hydrothermal alteration was late and gives the rhyolite a tan to brown color. Mostly unaltered, gray rhyolite was also documented. Initial geochemical testwork, presented in Section 13, suggests that the gray and pink rhyolite units have the highest REE content, averaging between 554 and 615 parts per million (ppm) total REE + Yttrium (Y). Red and tan rhyolites, which may be strongly vapor-phase altered, contain about 8% lower abundance of REE and the brown rhyolite, which may be altered hydrothermally or by groundwater, contains about 23% less REE than the gray and pink varieties.” (Hulse and others (2014)) “Round Top rhyolite is enriched in Heavy Rare Earth Elements (HREEs). Statistical review of the current data shows that an estimated 70% of the total REE’s grade being HREEs. REE mineralization occurs primarily as disseminated microcrystals of varieties of fluorite (such as yttrium-rich yttrofluorite) where HREEs have substituted for calcium, and as other REE-bearing accessory minerals. REE minerals occur mainly in vugs and as crystal coatings, suggesting late-stage crystallization from an incompatible element-rich fluid. Other incompatible elements were concentrated in these late magmatic fluids. Uranium occurs as fine disseminated grains of uraninite and coffinite. Niobium-tantalum bearing columbite is relatively abundant. Zircon also is relatively abundant and is the mineral containing the zirconium and hafnium. Several unidentified tin minerals are present and thorium is contained in thorite and within zircon.” (Hulse and others (2014))
Published resource estimates
| Material | Class | Amount | Grade | Contained | As of | Reference |
|---|---|---|---|---|---|---|
| hafnium oxide (HfO2) | Measured plus Indicated | 48,900 t | — | 41,500 metric tons Hf | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| hafnium oxide (HfO2) | Inferred | 34,500 t | — | 29,300 metric tons Hf | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| tin dioxide (SnO2) | Measured plus Indicated | 84,400 t | — | 66,500 metric tons Sn | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| niobium oxide (Nb2O5) | Measured plus Indicated | 262,000 t | — | 183,000 metric tons Nb | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| thorium oxide (ThO2) | Inferred | 68,500 t | — | 60,200 metric tons Th | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| tin dioxide (SnO2) | Inferred | 60,100 t | — | 47,300 metric tons Sn | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| niobium oxide (Nb2O5) | Inferred | 184,000 t | — | 129,000 metric tons Nb | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| tantalum pentoxide (Ta2O5) | Inferred | 27,700 t | — | 22,700 metric tons Ta | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| total rare-earth oxide (TREO) | Inferred | 216,000 t | — | 216,000 metric tons TREO | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| uranium oxide (U3O8) | Inferred | 18,200 t | — | 15,400 metric tons U | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| thorium oxide (ThO2) | Measured plus Indicated | 97,500 t | — | 85,700 metric tons Th | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| total rare-earth oxide (TREO) | Measured plus Indicated | 304,000 t | — | 304,000 metric tons TREO | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| tantalum pentoxide (Ta2O5) | Measured plus Indicated | 39,400 t | — | 32,200 metric tons Ta | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| uranium oxide (U3O8) | Measured plus Indicated | 25,600 t | — | 21,700 metric tons U | Jan 1, 2013 | Hulse and others (2014), Pages 90-91, Table 14-7 — Hulse, D. E. ,et al., 28-April-2014, NI 43-101 Amended Preliminary Economic Assessment Round Top Project Sierra Blanca, Texas: Prepared for Texas Rare Earth Resources: Gustavson Associates, 206p. |
| potassium (K) | Measured plus Indicated | ≈364,000,000 t | 3.3 percent | 12,000,000 metric tons K | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| hafnium (Hf) | Inferred | ≈735,000,000 t | 77.33111 kilograms per metric ton | 56,800 metric tons Hf | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| lithium (Li) | Measured plus Indicated | ≈364,000,000 t | 458.33111 kilograms per metric ton | 167,000 metric tons Li | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| praseodymium (Pr) | Measured plus Indicated | ≈364,000,000 t | 10.27111 kilograms per metric ton | 3,740 metric tons Pr | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| manganese (Mn) | Measured plus Indicated | ≈364,000,000 t | 471.28111 kilograms per metric ton | 172,000 metric tons Mn | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| tantalum (Ta) | Measured plus Indicated | ≈479,752,000 t | 67.2 grams per metric ton | 32,200 metric tons Ta | Jan 1, 2014 | Hulse and others (2014), Page 91, Table 14-7 — Hulse, D.E., Newton, M.C., III, and Malhotra, D., 2014, Amended NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for Texas Rare Earth Resources [Effective date November 30, 2013]: Gustavson Associates, LLC, 206 p., accessed April 24, 2018, at https://sedar.com. |
| aluminum (Al) | Measured plus Indicated | ≈364,000,000 t | 6.56 percent | 23,900,000 metric tons Al | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| scandium (Sc) | Measured plus Indicated | ≈364,000,000 t | 0.68111 kilograms per metric ton | 250.1 metric tons Sc | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| scandium (Sc) | Inferred | ≈735,000,000 t | 0.71111 kilograms per metric ton | 520.1 metric tons Sc | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| zirconium (Zr) | Measured plus Indicated | ≈364,000,000 t | 1104.09111 kilograms per metric ton | 402,000 metric tons Zr | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| hafnium (Hf) | Measured plus Indicated | ≈364,000,000 t | 79.36111 kilograms per metric ton | 28,900 metric tons Hf | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| dysprosium (Dy) | Inferred | ≈735,000,000 t | 29.61111 kilograms per metric ton | 21,800 metric tons Dy | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| thorium (Th) | Inferred | ≈341,898,000 t | 176.13 grams per metric ton | 60,218 metric tons Th | Jan 1, 2014 | Hulse and others (2014), Page 91, Table 14-7 — Hulse, D.E., Newton, M.C., III, and Malhotra, D., 2014, Amended NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for Texas Rare Earth Resources [Effective date November 30, 2013]: Gustavson Associates, LLC, 206 p., accessed April 24, 2018, at https://sedar.com. |
| praseodymium (Pr) | Inferred | ≈735,000,000 t | 9.97111 kilograms per metric ton | 7,330 metric tons Pr | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| tin (Sn) | Measured plus Indicated | ≈364,000,000 t | 137.51111 kilograms per metric ton | 50,100 metric tons Sn | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| sodium (Na) | Inferred | ≈735,000,000 t | 0.95 percent | 7,000,000 metric tons Na | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| gallium (Ga) | Measured plus Indicated | ≈364,000,000 t | 65.8111 kilograms per metric ton | 24,000 metric tons Ga | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| neodymium (Nd) | Inferred | ≈735,000,000 t | 27.55111 kilograms per metric ton | 20,200 metric tons Nd | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| beryllium (Be) | Measured plus Indicated | ≈364,000,000 t | 32.15111 kilograms per metric ton | 11,700 metric tons Be | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| uranium (U) | Inferred | ≈735,000,000 t | 8.38111 kilograms per metric ton | 6,160 metric tons U | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| zirconium (Zr) | Inferred | ≈735,000,000 t | 1049.38111 kilograms per metric ton | 771,000 metric tons Zr | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| potassium (K) | Inferred | ≈735,000,000 t | 3.21 percent | 23,600,000 metric tons K | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| niobium (Nb) | Measured plus Indicated | ≈364,000,000 t | 164.58111 kilograms per metric ton | 59,900 metric tons Nb | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| sodium (Na) | Measured plus Indicated | ≈364,000,000 t | 3.77 percent | 13,700,000 metric tons Na | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| tin (Sn) | Inferred | ≈735,000,000 t | 134.94111 kilograms per metric ton | 99,200 metric tons Sn | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| yttrium (Y) | Inferred | ≈735,000,000 t | 195.84111 kilograms per metric ton | 144,000 metric tons Y | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| iron (Fe) | Measured plus Indicated | ≈364,000,000 t | 1.04 percent | 3,790,000 metric tons Fe | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| samarium (Sm) | Inferred | ≈735,000,000 t | 9.85111 kilograms per metric ton | 7,240 metric tons Sm | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| dysprosium (Dy) | Measured plus Indicated | ≈364,000,000 t | 30.33111 kilograms per metric ton | 11,000 metric tons Dy | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| beryllium (Be) | Inferred | ≈735,000,000 t | 18.22111 kilograms per metric ton | 13,400 metric tons Be | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| lutetium (Lu) | Inferred | ≈735,000,000 t | 8.49111 kilograms per metric ton | 6,240 metric tons Lu | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| tantalum (Ta) | Inferred | ≈341,898,000 t | 66.4 grams per metric ton | 22,700 metric tons Ta | Jan 1, 2014 | Hulse and others (2014), Page 91, Table 14-7 — Hulse, D.E., Newton, M.C., III, and Malhotra, D., 2014, Amended NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for Texas Rare Earth Resources [Effective date November 30, 2013]: Gustavson Associates, LLC, 206 p., accessed April 24, 2018, at https://sedar.com. |
| magnesium (Mg) | Measured plus Indicated | ≈364,000,000 t | 0.03 percent | 110,000 metric tons Mg | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| terbium (Tb) | Measured plus Indicated | ≈364,000,000 t | 3.46111 kilograms per metric ton | 1,260 metric tons Tb | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| iron (Fe) | Inferred | ≈735,000,000 t | 0.82 percent | 6,000,000 metric tons Fe | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| neodymium (Nd) | Measured plus Indicated | ≈364,000,000 t | 27.88111 kilograms per metric ton | 10,100 metric tons Nd | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| gallium (Ga) | Inferred | ≈735,000,000 t | 16.96111 kilograms per metric ton | 12,500 metric tons Ga | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| thorium (Th) | Measured plus Indicated | ≈479,752,000 t | 178.66 grams per metric ton | 85,712 metric tons Th | Jan 1, 2014 | Hulse and others (2014), Page 91, Table 14-7 — Hulse, D.E., Newton, M.C., III, and Malhotra, D., 2014, Amended NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for Texas Rare Earth Resources [Effective date November 30, 2013]: Gustavson Associates, LLC, 206 p., accessed April 24, 2018, at https://sedar.com. |
| samarium (Sm) | Measured plus Indicated | ≈364,000,000 t | 10.06111 kilograms per metric ton | 3,660 metric tons Sm | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| aluminum (Al) | Inferred | ≈735,000,000 t | 6.52 percent | 47,900,000 metric tons Al | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| magnesium (Mg) | Inferred | ≈735,000,000 t | 0.01 percent | 74,000 metric tons Mg | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| lithium (Li) | Inferred | ≈735,000,000 t | 445.2111 kilograms per metric ton | 327,000 metric tons Li | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| manganese (Mn) | Inferred | ≈735,000,000 t | 118.86111 kilograms per metric ton | 87,400 metric tons Mn | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| niobium (Nb) | Inferred | ≈735,000,000 t | 46.52111 kilograms per metric ton | 34,200 metric tons Nb | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| yttrium (Y) | Measured plus Indicated | ≈364,000,000 t | 213.97111 kilograms per metric ton | 77,900 metric tons Y | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| lutetium (Lu) | Measured plus Indicated | ≈364,000,000 t | 8.79111 kilograms per metric ton | 3,200 metric tons Lu | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| uranium (U) | Measured plus Indicated | ≈364,000,000 t | 31.77111 kilograms per metric ton | 11,600 metric tons U | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
| terbium (Tb) | Inferred | ≈735,000,000 t | 3.30111 kilograms per metric ton | 2,430 metric tons Tb | Jan 1, 2019 | Hulse and others (2019), Page 96, Table 14-10 — Hulse, D.E., Malhotra, D., Matthews, T., and Emanuel, C., 2019, NI 43-101 preliminary economic assessment Round Top project, Sierra Blanca, Texas, prepared for USA Rare Earth LLC and Texas Mineral Resources Corp. [Filing date July 1, 2019]: Gustavson Associates, LLC, 218 p., accessed October 17, 2019, at http://usarareearth.com/. |
Exploration and site history
- Development — Trial mining; Underground drift and drilling, 1988 (Hulse and others (2014))
- Exploration — Surface sampling, 2010–2014 (Hulse and others (2014))
- Exploration — Aeroradiometric survey, 2010–2014 (Hulse and others (2014))
- Exploration — Exploratory drilling, 2010–2014 (Hulse and others (2014))
- Exploration — Stream sediment surveying, 2010–2014 (Hulse and others (2014))
- Exploration — Gravity surveying, 2010–2014 (Hulse and others (2014))
- Exploration — Drilling; Cyprus Metals takes over, 1987 (Hulse and others (2014))
- Exploration — Logging cuttings from R.C. drilling, 2010–2014 (Hulse and others (2014))
- GeolMinOcc: “The Round Top rhyolite was divided into five different alteration phases based on the intensity of hematitic and hydrothermal alteration: gray rhyolite, pink rhyolite, red rhyolite tan rhyolite and brown rhyolite in the order of least to most altered. Hematitic alteration is a replacement of the magnetite by hematite and gives the rhyolite a red to pink color. Hydrothermal alteration was late and gives the rhyolite a tan to brown color. Mostly unaltered, gray rhyolite was also documented. Initial geochemical test work, presented in Section 13, suggests that the gray and pink rhyolite units have the highest REE content, averaging between 554 and 615 parts per million (ppm) total REE + Yttrium (Y). Red and tan rhyolites, which may be strongly vapor-phase altered, contain about 8% lower abundance of REE and the brown rhyolite, which may be altered hydrothermally or by groundwater, contains about 23% less REE than the gray and pink varieties.” (Hulse and others (2014))
- Exploration — Exploration at the site has consisted of drilling, gravity surveys, surface sampling, and stream sediment surveys, 1970–2019 (Hulse and others (2019))
- Evaluation — NI 43-101 compliant report released, 2014 (Hulse and others (2014))
- Evaluation — NI 43-101 compliant report released, 2019 (Hulse and others (2019))
- Evaluation — NI 43-101 compliant report released, 2012 (Hulse and others (2012))
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
- U.S. Geological Survey · published Feb 22, 2021 · retrieved Aug 15, 2026 · archive unavailable: No Wayback snapshot verified for the ScienceBase item on the 2026-08-15 import; archive capture queued for a weekly pass