Copyright © 2006 by Ana Minerva Bonilla Updated: August 29, 2006 12:31
Reprinted by permission at http://theweekendminer.com
THE WEEKEND MINER
Rediscovering American Mineral Resources
THOUGHTS FROM THE “OLD MINER”
Antimony
Chemically, Antimony is considered a “semi-metal”, with an Atomic Number of 51, an Atomic Weight of 121.75, and a density of 6.68 g/ml. There are 35 isotopes; 104 & 105 and 107 through 136, with 121 and 123 being considered stable. The 35 number comes about because 120, 124 and 126 each have two isotropic configurations. The decay products are Tin for the 104 through 120 isotopes and Tellurium for 122 through 135 isotopes.
Although Antimony has been used by man for over 6,000 years, it is relatively unknown to the general public, even today. Antimony sulfide, in the form of the mineral stibnite and Lead sulfide (galena) formed the base of Kohl. Kohl was the thick, black paste that was use by the ancient Egyptians as a cosmetic to line the eyes and color eyebrows. Antimony was named “Stibium” by Pliny the Elder; a name that is still reflected in its chemical symbol, “Sb”. It was named “antimonium” by the eighth-century Arabian alchemist Jabir, because it was always found with other metals. “Antimonium” came from the Greek words “anti”, or against, and “monos”, to be alone. Today we usually use the word Antimony to describe it, although minerals containing Antimony still use the root-word Stibnite in many of their names.
Antimony became important with the printing press, where the type blocks were cast from Lead. Lead, by itself, wasn’t hard enough to wear well, so Antimony was added to harden it. It is still used for this purpose in cast bullet lead today, with the exception of black-powder round-balls, where you don’t want them too hard, so you can get them down the barrel easier. The English used an Antimony-Tin alloy, called “Britannia Metal” for a lot of their early dishes, eating utensils and things like candlesticks and small figurines. It was probably a lot better for them than lead, which was also widely used in the Mediterranean area. Antique collectors frequently find Antimony alloys in metal utensils and decorative items from the US Colonial Period.
Today Antimony’s is used in the US in both its compound and metallic forms. As a compound an estimated 35,000 tons are used each year; about 2/3 of that amount as flame-retardants, for primarily organic polymers. Other major uses, in the compound form, with about 10% each, are as plastics stabilizers and catalysts; use in the ceramics and glass industry, where it is used as a fining agent and decolorant for high-quality glass for applications like CRTs (cathode ray tubes); and as a pigment. In the metallic form only about 4,000 tons per year are used, 2/3 of this in batteries. On a worldwide basis about 60% of Antimony produced is used as flame-retardants, 20% in batteries and alloys and about 20% in other applications.
Production is centered in China, which in 2004 produced 100,000 MT of the worldwide production of 112,000 MT that year. Other producers are South Africa with 5,000 MT and Bolivia and Tajikistan, with about 2,500 MT each. While numerous other materials can substitute for Antimony in most applications, the glass-fining use for CRTs and other high-quality glass applications for electronics tends to be fairly exclusive to Antimony. The access to and potential capture of this technology may be why China has chosen to dominate production of Antimony.
The US does have one small producer of Antimony remaining. That is U.S. Antimony Corp., in Thompson Falls, Montana. They produce somewhere between 750 and 1,000 MT of Antimony product per year. In September, 2004, USAC announced that it was foregoing Antimony sales due to a shortage of raw materials. In an article in American Metal Market, September 14, 2004, pages 1 and 2, the shortage was blamed on Chinese Antimony producers raising prices and putting other Antimony oxide producers out of business, increasing Chinese demand and falling Chinese supply.
This shortage of raw material and the nature of Antimony deposits might make this one of the metals small miners might be interested in. The USGS Open File Report 03-019, page 10, cites a 1985 work by Plunkert from the US Bureau of Mines Bulletin 675, that describes Antimony mining as: “The typically small ore bodies from which Antimony is produced as a principal product do not lend themselves to exploration on a large scale. When possible, they are mined by open pit methods. Underground Antimony mines are typically small, the ore body being accessed by a short adit or shaft, and are developed by drifting along the vein and stoping by simple overhand methods. Mines in which Antimony is produced as a byproduct use the large-scale methods common to base- and precious-metal mines.” This is reinforced on page 32: “Known Antimony deposits in the United States tend to be small irregular deposits that do not lend themselves to large-scale low-cost mining methods.”
Antimony mines have proliferated throughout the southwestern US. In the Southern California areas that we have loaded to the Weekend Miner Database, we find Antimony mines identified in Inyo, Kern and San Bernardino Counties. In Inyo County Antimony is found at the Bishop Antimony Mine, the Darwin Antimony Mine, the Old Dependable Antimony Mine and the Wild Rose Antimony Deposit. In Kern County Antimony is found at the Alice Mine, the Antimony Consolidated Mine, the Antimony Peak Mine, the Big Oscar Antimony Deposit, the Erskine Creek Deposits, Jawbone Canyon Mine, Jones and Wimmer Antimony Claim, the Little Caliente Spring area, the Mammoth Eureka Mine and the Rayo Mine. In San Bernardino County Antimony is found at the Antimony Mine, the Atolia Mine, the Desert Antimony Mine, and the Mountain Pass Antimony Mine. Its found in many other places in California and throughout the Southwest, possibly in commercial quantities. We will add additional mines to this section, as they are loaded to the database.
So you might have an idea how Antimony ores are processes I will tap Plunkert once again. He indicates that there are about 6 basic ways Antimony is extracted from its ores. The method used depends on the type of ore; sulfide, oxide or complex; and the grade of ore, which ranges from about 1.5% to over 60% by weight. Sulfide ores or concentrates in the 1.5% to 25% range tend to be roasted to produce Antimony oxide. Those in the 25% to 45% range are smelted to produce crude Antimony metal in blast-type furnaces. Sulfide ores in the 45% to 60% range are heated in a reducing atmosphere and the Antimony sulfide melted. It is separated from the gangue by pouring to get “crude Antimony”, usually in the 70% Antimony purity range. Some of the richest ores, those above 50%, are treated by the “Precipitation Process” or “English Process”, similar to the old “Cement Copper Process”, is usually carried out in crucible furnaces. In it the Antimony is displaced chemically from the molten sulfide by iron shavings or scrap, to yield an impure Antimony contaminated with iron and sulfur.
Oxide ores in the 30% Antimony range are usually reduced in blast-type furnaces to crude Antimony. Richer ores, 50% Antimony and more, are usually reduced in short rotary or reverberatory furnaces by charcoal. This usually gives a commercial or crude grade Antimony, that is often refined to 99%+ purity.
The complex ores or ores containing Antimony as a byproduct usually are smelted in blast furnaces. Some of the more difficult, complex ores are processed by selective leaching, followed by electrolysis; similar to the solvent exchange electrowon copper process. This generally produces a 93% to 99.5% purity Antimony metal.
With Antimony currently over $3.00 per pound, it might be something you should be aware of. If you find a high-grade source it might be worth pursuing commercially, even if only at a “small miner” level; and it might be good for the country.
UPDATE of August 16, 2006:
We must have quite a number of readers, based on the questions we are getting. I know some websites that really don’t get any, so it is nice to hear from you.
I got a number of questions regarding how to sell Antimony; mostly what form or forms is it salable in? I really didn’t know so I contacted a couple of experts.
The fellows at Amalgamet Canada gave me the following; which I believe is for a Chinese concentrate:
60% Sb minimum
0.5% As + Pb combined; usually 0.25% each; ideally 0.15% max. each
30 ppm Se max
20 ppm Hg max
trace Te (less than 10 ppm)
10ppm max. Sn
trace Bi (less than 10 ppm)
S usually 24% min.
The Western US and Mexico expert has got to be John Lawrence, the President CEO of US Antimony in Thompson Falls, MT. He was nice enough to answer my inquiry personally. Here is the text of his reply to me: “We purchase either Antimony concentrates, hand sorted ore, or various residues and metal. The concentrates and hand sort specifications are:
60% Antimony (Sb)
less than 0.2% Arsenic (As)
less than 0.2% Lead (Pb)
less than 50 ppm Selenium (Se)
low Bismuth (Bi)
low Tellurium (Te)
For this we would pay 50% of the LMB Rotterdam quotation for Antimony metal. For lesser grades or higher impurities we would pay less. The price would be FOB our plant at Thompson Falls, Montana, or Madero Coahuila, Mexico.”
(Note: The price, at the time of his e-mail back to me was $5,353.13 per Metric Tonne – 2,204.62 pounds; or about $2.43 per pound. This would make the prime ore worth over $1.00 per pound. Not bad for picking up rocks and helping keep American industry going and growing.)
There you have it; now you know as much about this as I do. Hope it helps.