Geology, Geology Talk

A visit to the dentist

A visit to the dentist has made Bill Langer all excited about fluorspar – anything to avoid the pain of dental work!

You know the drill. Recently I was reclining in the dentist chair while a hygienist jabbed a sharp pick into my gums. She paused and asked: “So you’re a geologist. Do you look for gold?”

“No,” I answered between clenched teeth, “I study industrial minerals, like fluorite, which is used to make the fluorine you put on my teeth.”

I hoped she would continue the dialogue and stop jabbing my gums. Besides I love to talk about fluorspar because it exemplifies the trials and tribulations of industrial mineral development.

Fluorspar, like most industrial minerals, has a relatively low value compared with metallic ores mined under similar conditions. The margins of profit are small and it commonly requires exceptionally good management to profitably conduct any fluorspar (or any other industrial mineral) mining operation.

In the late 1800s, fluorspar was used chiefly in the manufacture of opalescent glass and the preparation of fluoride-bearing chemical compounds. However, in the early 1900s, the use of fluorspar increased when it replaced some of the limestone as a flux in the manufacture of open hearth steel.

Most steel production was located in the contiguous American states of Pennsylvania, Ohio, Indiana and Illinois. Fluorspar deposits in Illinois and Kentucky that were near those markets and were accessible to water or rail transportation had a huge advantage over those not so favourably situated.

So, while there is high grade fluorspar in many western US states, during the early 1900s their development was handicapped by the costs of long transport. The quantity of fluorspar in a deposit is critical.

In the early 1900s, a commercial deposit needed to produce at least a railcar load of marketable fluorspar a day and have at least a 15-year life.Unscrupulous promoters swindled prospective producers out of large sums of money for the purchase of leases on properties that did not contain fluorspar in sufficient quantity to warrant development.

Fluorspar may contain impurities that have to be eliminated for many uses. A log washer commonly was used to clean fluorspar, and a convenient supply of water was essential. In arid portions of America’s west, fluorspar was cleaned by hand cobbing, which entailed much manpower and large amounts of waste. This further reduced the competiveness of western fluorspar operations.

In the second quarter of the 19th century, the production of steel drove the fluorspar market. But new applications continued to be developed, including chlorofluorocarbon (CFC or freon) used in refrigerators and air conditioners.

Meanwhile, cheaper imports replaced US production and by the middle of the 20th century over a quarter of the fluorspar used in the US was imported.

In the third quarter of the 20th century the markets for fluorspar exploded.

Fluorine found its way into applications including aerosols, anaesthesia, plastics, rubber, satellites, Teflon and toothpaste. The list of uses kept getting longer and longer. In 1974, the demand for fluorspar peaked. But 88 per cent of the demand was met by imports.

In the last quarter of the 20th century, fluorspar’s use in steelmaking decreased dramatically and the production of CFC was stopped because of its impact on the world’s ozone.

The last US fluorite mine closed in 1995, signaling the end of 158 years of US fluorite mining.

Today the US is totally dependent on imports of fluorspar, a mineral that once was deemed vital to the United States for security and economic reasons.

The good news is that mining is expected to begin again in Kentucky.

Did I tell you the hygienist’s response to my mention of fluorspar? Jab, jab, jab! If only I had studied gold!

Bill Langer is a consultant geologist.

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