Measurable quantities of tantalite and to a lesser extent microlite accumulate in our recreational flumes or sluice boxes daily. A U.S. Bureau of Mines Regional File Report dated 1943 reported Mr. Silas Morefield produced about 1400 pounds of tantalite, manganotantalite, microlite, and columbite, with some of it sold for specimens. The 1948-1949 U.S. Bureau of Mines work on the occurrence of tantalite, bulk testing, and beneficiation methods are presented in Report of Investigation 5001, Morefield Pegmatite Mine, Amelia, VA, by R.W. Geehan and dated November 1953.
Most of their work focused on the complex pegmatite zone that occurs on the 15 acre tract that comprises the active mining area. USBM noted that columbite-tantalite and microlite are scattered through the rare-mineral zone from just above the 100 foot level to the surface open cut. Of great interest now is whether a complex zone underlies the simple pegmatite exposed in the new 65 acre tract and whether the simple pegmatite has recoverable quantities of tantalum minerals.
USBM test pits and trenches established a strike-length over a distance of 1,000 feet and drill holes disclosed the dike at a dip length of 225 feet (Figure 8). From this, they determined the explored portion of the dike contained 47,130 tons in the weathered zone and 157,518 tons in the unaltered zone. However, later trenching by the past owner indicates the dike continues southeast to Virginia county route 628, approximately 750 feet beyond the ore reserve blocking done by USBM. Figure 8 was taken from the Bureau of Mines RI 5001 report and recent formation has been added.
Figure 9 shows the ore reserve tonnage determined by the Bureau of Mines and published in their Final Report, Project 3002 – Morefield Mine, February, 1945.
Foote Mineral Co. took six surface grab samples on November 17, 1980 and reported 0.18 pounds per ton tantalum and 0.90 pounds per ton niobium. The bulk sample taken by the USBM came from a depth of about 75 feet in a large raise and diamond drill station located just southwest of the main shaft. Beneficiation tests were conducted at the Eastern Experiment Station at College Park , Maryland . The tantalite-columbite was determined by grain count and reported to be, “0.1 percent by grain count and equivalent to about 0.2percent by weight or about 4 pounds per ton”. They found from hand-picked specimens and analysis of the tantalite that the mineral contained 45.7 percent Ta2O5, 31.2 percent Nb2O5, and 2.0 percent Ti02. The concentrates were obtained from a 1300 pound sample using tables, magnetic and electrostatic separation. It was estimated to contain 43.7 percent Ta2O5. This is a much higher concentrate grade than the 30 percent minimum Ta2O5 content used as the basis for commercial sales. Morefield mine concentrate would bring a higher price per pound.
In May, 2002, Morefield Gem Mine, Inc. retained the NCSU Minerals Research Laboratory at Asheville , NC . To do a metallurgical test based on the USBM work. They
limited their test to magnetics using a “PermRoll Separator and a Carpco magnetic separator. The tests were on a 600 pound “run-of-mine” sample and a quantity of sluice box concentrates. The run-of-mine sample had a calculated head grade of 0.06 percent Ta. This is equal to 1.2 pounds of tantalum per ton. An analysis of pure tantalite was not made, but using the USBM number for Ta2O5 in handpicked tantalite of 45.7 percent, this would equal 2.6 pounds of tantalite per ton in the test sample.
While the work done by the U.S Bureau of Mines, Foote Mineral Company, and the North Carolina State University , Mineral Research laboratory does not confirm the existence of a commercial tantalum deposit, the collective work does indicate more investigation is warranted to determine if a minable deposit exists.
Figure 10 shows a tantalite crystal in complex pegmatite, NQ diamond drill core. This diamond drill hole cut the pegmatite on the 45 foot level southwest 130 feet from the main shaft.
As stated earlier, heavy minerals accumulate in the sluice boxes (flumes) used by schools and the public. Figure 11 is an example of panned heavy minerals consisting of tantalite, microlite, monazite, garnet, and trace zircon. The particle size shown is the plus 20 mesh screen fraction.
Pricing of tantalite ore or concentrate
Tantalite pricing is shown generally as the spot price. However, much tantalite is sold by contract for prices that can vary considerably. When demand surges, the contract price more accurately reflects the spot price. In times of slower economy, contracts may settle for less than the spot price.
International prices for tantalite ore may be based on Dollars, Euros, etc. per kilogram of contained tantalum, or Dollars, Euros, etc. per kilogram of 30 percent contained Ta2O5. Or one may find prices posted on some websites in Dollars (US or CN) per pound Ta2O5 and the purity unspecified. The various ways of pricing concentrates makes it cumbersome to convert posted prices to an understandable number. The following prices in Dollars per kilogram were taken from Infomine.com-InvestmentMine. They were converted to Dollars per pound 30% tantalum pentoxide, then to 43.7% tantalum pentoxide to reflect the concentrate grade estimated by the U.S. Bureau of Mines for Morefield mine. It also shows the rather large cyclical price range over the year 2013 but with improvement in 2014.
| ||Ta2O5 content ||30% ||30% ||43.7% |
|April ||2013 ||$262/kg ||$119/# ||$173/# |
|Oct. ||2013 ||$215/kg ||$98/# ||$142/# |
|Dec. ||2013 ||$158/kg ||$72/# ||$103/# |
|July ||2014 ||$207/kg ||$94/# ||$137/# |
Another benefit to Morefield mine tantalum is its origin in the USA guarantees it is ‘conflict-free’ and the cost of guaranteeing the chain of ownership is minimal compared to African tantalite. Tantalum concentrate/ore is often referred to as ’Coltan’.
Morefield Mine Permitting and Inspection
Morefield mine is inspected by the Virginia Department of Mines, Minerals, and Energy – Division of Mineral Mining; the federal Mine Safety and Health Administration (MSHA); and the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF). The 65 acre tract is zoned heavy industrial M-2 and the 15 acre mine site is zoned Rural Preservation RP-5. The Virginia Division of Mineral Mining mine permit number is 13378AC. The MSHA mine number is 44-06971.
Why consider tantalum when none is mined in the United States ? Known deposits have been uneconomic to mine. However, as prices improve and foreign sources possibly become less reliable, small US deposits are worth re-evaluating.
Eight largest tantalum producers 2013
|Source John F. Papp, U.S.G.S. |
|1 Rwanda ||150 MT |
|2 Brazil ||140 MT |
|3 Democratic Republic of the Congo ||110 MT |
|4 Nigeria ||60 MT |
|5 Canada ||50 MT |
|6 Mozambique ||40 MT |
|7 Burundi ||30 MT |
|8 Ethiopia ||10 MT |
A Hypothetical Hard Rock Tantalum Mine Similar to Morefield pegmatite.
|Length 1000’ ||Density ||12 FT3/Ton |
|Width 12’ ||Grade 1.5#/Ton Ta2O5 (0.075%) |
Total tonnage = 300,000 short tons
Total Ta2O5 = 450,000#
Mine and Mill Recovery 70%
Recovered mine ore = 270,000 short tons
Recovered Ta2O5 = 315,000#
Mine life 7 years
Mining rate 150 TPD, 252 days/year
Yearly mine ore production = 37,800 short tons
Yearly Ta2O5 production = 56,700#
= 28.3 short tons
Yearly tantalum production = 28.3 short tons X 81.89% Ta/Ta2O5 = 23.2 short tons = 23.2 short tons X 0.9072 st/mt = 21.0 metric tons
. The hypothetical small mine as described above would produce, annually, equivalent to the entire production of the eighth largest foreign tantalum producing nation.
Not considered is the total cost of development, mining, processing, shipping and capitalization. Those costs have not been estimated for a deposit similar Morefield pegmatite and 1.5#/ton Ta2O5 may not produce sufficient sales to cover costs or produce an acceptable profit.