The state of Nevada is quickly becoming the leading source of lithium in the USA and beyond. In the state there will soon be three major types of lithium ore beneficiation- Brine evaporation, hard rock extraction and lithium clay extraction. Nevada already has in excess of 180,000 active mining claims amounting to 49 % of the total BLM national inventory. In addition to this, Nevada has “198 authorized mining plans of operations, and 282 active exploration notices.” Nevada has a long history of fruitful gold and silver mining.

Nevada had earlier won the gold deposit lottery with the Carlin Trend occupying much of the northwestern section of the state. The Carlin Trend has become an archetype in gold mining. These deposits are often described as Carlin-type “invisible gold” ore deposits. Such a deposit is characterized as sediment hosted and disseminated [Editor: disseminated seems like a bummer]. Gold in such deposits are typically invisible and often only detected by lab analysis. According to Wikipedia, most of the gold mines in the Great Basin of the western US are of the Carlin-type.

But, enough about gold and on to lithium

After 6 years of regulatory scrutiny, a new lithium-boron open-pit mining operation in Nevada operated by Australian mining company ioneer has just been approved by the Bureau of Land Management, BLM, for Rhyolite Ridge. The mine is located in the Basin and Range Province near the southwest border of Nevada and California.

The old joke used to be that a mine is a hole in the ground with a liar standing at the top. With the independent economic evaluations available today as part of the disclosure to investors, the likelihood of being duped by fake or salted deposits has dropped considerably. However, the market value of the ore in the future is still subject rapid and unpredictable change.

If you find yourself flying over Nevada on a clear day, you can easily see the basin and range features of the terrain. Nevada occupies only a small part of the total area. The basin and range province extends north to the Columbia Plateau and south into the Central Mexican Plateau.

Rhyolite Ridge Lithium-Boron Project

The BLM approval opened up $1.19 billion of potential funding of which $700 million is from a US government loan. According to Mining.com, Rhyolite Ridge is the first new lithium mine in 60 years and the first new boron mine in the last century in the US. [Note: I have to assume “new” means new hard rock mine as opposed to brines or evaporites] While the approval by BLM has opened some doors to funds, not everyone is convinced of the major investor’s liquidity.

So, what is rhyolite?

I can’t improve on the definition found in Wikipedia, so I’ll just quote it with the links intact-

Rhyolite (/ˈraɪ.əlaɪt/ RY-ə-lyte)^[1][2][3][4] is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent of granite.

Its high silica content makes rhyolitic magma extremely viscous. This favors explosive eruptions over effusive eruptions, so this type of magma is more often erupted as pyroclastic rock than as lava flows. Rhyolitic ash-flow tuffs are among the most voluminous of continental igneous rock formations.

If you have ever seen molten glass and noticed its high viscosity, this gives an idea of what high silica content does to lava. The higher viscosity provided by the silica component suppresses the release of gases until nearer the surface where they are released as bubbles with vigor. It is very much like a comparison between boiling pasta water and boiling marinara sauce. The marinara sauce spatters badly due to its viscosity but the pasta water just does a rolling boil.

The Rhyolite Ridge lithium-boron (LiB) deposit is said by some to be the only known LiB deposit in the US and only one of two known in the world.

“The Rhyolite Ridge mine will run for 22 years. It will produce 22,000 tonnes of lithium carbonate a year. That’s enough to power 370,000 electric vehicles. It will also produce 170,000 tonnes of boric acid, according to the company. The boron contributes 30% to 40% of the mine’s revenue, providing a buffer against lithium market volatility.” –Mining.com

Around the world new economic lithium deposits are being discovered now and then, and a few are being readied for mining. It was announced recently that BLM has approved operations at the Rhyolite Ridge Lithium-Boron Project in southwestern Nevada.

What is interesting about this Rhyolite Ridge project is that it aims to produce both lithium and boron. I’m not an engineer so maybe I’m overly impressed, but the processing plant they propose seems very clever. They will produce their own sulfuric acid from sulfur and extract waste heat for use in generating steam for evaporation of the extracts and electricity. They are completely off the energy grid.

The extracted ore, now called ROM or run-of-mine, is transported to the plant straight from the mine and sized by crushing to 20 mm pieces. The crushed ROM is then taken to a series of sulfuric acid extraction vats and leached for ~ 7 days. The pregnant leach solution containing the lithium, boron and soluble impurities is then taken to evaporators with repeated crystallizations and, using differential solubility, separates the lithium component from the boric acid. In the end they produce lithium carbonate. The video does show a soda ash (sodium carbonate), Na₂CO₃, silo so I assume that is where the carbonate comes from to produce lithium carbonate, Li₂CO₃ and to neutralize residual sulfuric acid.

Silver Peak Lithium Brine

Of interest is the nearby Silver Peak lithium brine operation operated by Albemarle just a few miles to the north of Rhyolite Ridge. The Google Maps image below shows the evaporation ponds at the Silver Peak lithium operation. Silver Peak produces both technical grade lithium carbonate and lithium hydroxide.

McDermitt Caldera: Thacker pass

Another large lithium deposit was discovered in the McDermitt Caldera along the Nevada-Oregon border. Within the caldera is the Thacker Pass Lithium Mine. This lithium deposit was approved for open-pit mining by BLM on January 15, 2021, though it has been plagued by protests and an injunction. As with the rest of the McDermitt Caldera lithium, the Thacker Pass lithium is described as a lithium rich clay deposit. This is unique for lithium mines since brine extraction and hard rock mining of spodumene have been the norm. Thacker Pass’ lithium deposit is the largest known volcano sedimentary deposit in the US at an average grade of 0.22 %.

In 2023 GM invested $650 million in the Canadian Lithium Americas Corp. The Thacker pass operation is through its wholly owned subsidiary Nevada Lithium, LLC, which is responsible for production. Car giant GM’s investment gives them exclusive access through the first phase of production. Lithium Americans has received a conditional approval for a $2.2 billion loan from the US Department of Energy.

The Thacker Pass measured and indicated lithium resources are 13.7 million tons of lithium carbonate equivalent. Lithium Americas calculates that the recoverable lithium is worth $3.9 billion.

Interestingly, the McDermitt Caldera is possibly the oldest of a sequence of calderas produced by the Yellowstone Hotspot. The McDermitt Caldera amounts to a lava dome that collapsed ~16.4 million years ago forming a large caldera within which several smaller calderas have formed and in which later filled with water forming a lake over the tuffaceous ash. Over time the lake produced sediments that were deposited on the floor of the lake. The source rock is rhyolite which is usually the case in the state.

Briefly, the lithium clay is excavated, gravel and rocks are removed, and the clay is suspended in water to form a slurry. The slurry is leached by adding sulfuric acid that is produced on-site and the lithium in the ore is extracted into the acidic liquor. Finally, the dissolved lithium is recovered as lithium carbonate and lithium hydroxide. Gangue material is deposited back into the excavated sections of the mine.

The McDermitt caldera contains many breccia and fracture zones and associated with these are deposits of other metal ores. Specifically, mercury from cinnabar ore bodies and uranium from autunite (uranyl, U⁶⁺) (Ca(UO₂)₂(PO₄)₂·10–12H₂O) and pitchblende (uranate, UO₂, U⁴⁺) ore bodies. Mercury reserves in the caldera, according to USGS, are estimated to be 400,000 flasks.

A Mercurial Rambling

Mercury has been packaged (and still is) at 76 pounds to the flask. This measure got its name from the mining and smelting of cinnabar in the mountains of Peru. One site was particularly rich- Huancavelica, Peru. The Spaniards had known prior to their arrival to the New World that liquid mercury could dissolve gold from ore to produce what we now know as a mercury amalgam. With very strong heating the mercury could be driven off as vapor to recover the precious metal.

Spain had its own cinnabar mine in what is now Almadén, Spain, which produced over 250,000 tonnes of mercury. The Spaniards had considerable experience with mining, refining and using mercury prior to discovery of it in the new world. Mercury was quite valuable to the Spaniards but they were faced with transporting it from, say, Huancavelica, Peru, to the Carribean coast where their ships could load the mercury and distribute elsewhere. Anecdotally, it has been estimated that for every ounce of gold produced in the new world, ten ounces of mercury were consumed.

Luckily for the 49er gold rush miners, cinnabar had previously been discovered in California. You can actually visit the old New Almaden mine museum south of the Bay Area. It is worth a trip if you are in the area.

The Spaniards figured that a man could carry what turned out to be as much as 76 lbs of mercury through difficult terrain to the Caribbean coast. Even better for the Spaniards, they knew how much gold could be extracted per pound (or whatever unit) of the mercury they dispensed. This gave them an idea of how much gold to expect and closer control of the mines. By controlling mercury, they controlled who could use it for mining and how much gold they could recover.

Back to lithium

As of this writing, Albemarle is the largest producer of lithium in the US. But the largest known deposit in the US is at Thacker Pass. The Albemarle Silver Peak lithium brine operation is legally defined as placer mining whereas the Thacker Pass operation is lode mining. The word ‘legally’ is used because any claims filed are restricted to placer or lode mining- one does not transfer to the other.

A Word or Two About Rhyolite

Rhyolite is a type of volcanic rock characterized as a ‘fine-grained extrusive igneous rock‘. Its color can vary from pale light grey to pinkish when composed of mainly quartz and feldspar or dark when of a mafic, low silicate composition was present. A quiet eruption of lava gives a solid, denser rhyolite whereas in an explosive eruption can produce the vesicular pumice. The lower density of pumice allows it to float on water. Erupting volcanic islands can produce floating rafts of pumice in the nearby waters. As magma rises in the throat of a volcano, the pressure drops and dissolved gases can form bubbles which, if they fail to disengage from the magma completely, can be ejected into the cooler air and freeze into ‘foamy’ structure. [Note: the word ‘foamy’ is my own and earth science people cannot be blamed for this.]

A Bit More About McDermitt Caldera

The United States Geological Survey (USGS) published open-file report 76-535 in 1976 titled Geology and Ore Deposits of the McDermitt Caldera, Nevada-Oregon. A 1978 USGS open-file report by Newmont Exploration, Ltd., 78-926, James J. Rytuba and Richard K. Glanzman, Relation of Mercury, Uranium and Lithium Deposits to the McDermitt Caldera Complex, Nevada-Oregon, goes into greater detail on the three minerals.