The two North Carolina operations closed with the development of lower cost sources in Chile but could, should a massive demand materialize and prices rise as a result, be reactivated.
Based on figures used in the Lithium Panel report and later reserve data it is estimated, very approximately, that the FMC and former Foote operations contained reserves of 80,000 and 150,000 tonnes Li respectively at the time both operations were closed.
The Panel, based principally on Kesler’s very extensive work along the 48km long belt estimated a potential recoverable resource down to a depth of 1,500 metres of 375 million tonnes of ore at a grade typical of the area thus containing 2.6 million tonnes Li.
Other known pegmatite sources are small.
The Panel report listed tonnages for three brines – at Searles Lake, California, at Silver Peak, Nevada and the Great Salt Lake, Utah.
At Searles Lake lithium was recovered as a by-product from the commercial production of soda ash, potash and borax. The lithium was essentially a contaminant and with a process modification production ceased in 1978. It is highly improbable that lithium recovery will take place in the future. Silver Peak commenced production in the 1960’s pumping brines varying from 100 to 300 ppm Li. It continues to operate and the remaining economic reserves are estimated at 40,000 tonnes Li.
In the Great Salt Lake the overall tonnage of contained lithium approximates to 520,000 tonnes but the grade is very much lower than other brines considered as potential reserves in this report.
At the Salton Sea KGRA in southern California a brine with very high concentrations of potash, lithium, boron, zinc and lead is used to produce 288 megawatts of electric power.
A 30,000 tpa high grade zinc plant based on the brine has experienced technical problems but the brine also grades about 200 ppm Li and the throughput contains approximately 16,000 tpa Li. (William Bourcier, Lawrence Livermore National Laboratory, personal communication). Earlier (Duyvestein, 1992) calculated a similar figure of approximately 11,900 short tons of carbonate per 50 MW of capacity.
To put a reserve tonnage to the annual rate a 20 year life is assumed to give a figure of 316,000 tonnes Li.
There are other sites in the area with high lithium values.
Further north at the Mammoth Lakes geothermal field with a much lower lithium concentration, Lawrence Livermore Labs have a current project aimed at silica recovery which would be a first step in recovering lithium from brines of this nature
Collins (1978) estimated a possible reserve of 0.75 million tonnes of Li in one tenth of the area underlain by the Smackover Formation which extends through North Dakota, Wyoming, Oklahoma, east Texas and Arkansas. Other lithium-containing brines exist in the Paradox Basin, Utah.
At the McDermitt Caldera on the Oregon/Nevada border, Western Uranium Corporation are re-examining seven lenses of hectorite clay originally drilled by Chevron Resources.
Drilling at the most southerly site, the PCD lens, is confirming the tonnage and grade indicated by Chevron. This lens has a length of about 2 kms, a width of approximately one kilometer and a thickness of 100 metres under shallow overburden. Higher grade portions of the deposit grade over 0.35% Li and the cut off used in the reserve calculation is 0.275% Li.
Chevron reported that the total resource contained 23.9 billion lbs of carbonate – 2 million tonnes of Li and test work on recovery methods is currently being undertaken.
Hectorites are known to occur elsewhere in the western United States but no reserve data exist.