Phosphate Mining in Tunisia EarthCache
Thutmosis: It would appear that the Lezard Rouge train is no longer running.
Phosphate Mining in Tunisia
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Transport yourself to the Tunisian mining center of Metlaoui, 51 km north of Tozeur, and board the famed Lezard Rouge. Signs direct you to the train station. The train departs in the morning, takes you to the phosphate mine at the coordinates and returns.
The Red Lizard train is a century-old narrow-gauge railway once owned by the Bey of Tunis. It is an easy, popular ride through the spectacular Seldja Gorge, ending at the Kef Eddour open pit phosphate mine. The larger Kef Eschfair mine is located near by. Both are operated by the government-owned Compagnie des Phosphates de Gafsa. Most passengers go for the ride and the scenery alone. But for earthcachers some interesting geology awaits you.
After leaving Metlaoui, the train crawls across the flat desert and soon enters the low desert mountains comprised of uplifted sedimentary strata of limestone. The track follows a stream which has cut a gorge through the mountains. The water runs brown and cloudy, a legacy of the mining enterprises upstream. Midway into the gorge, the train stops and you will have a chance to disembark. See if you can find some of the chert nodules which have weathered from the surrounding rock. Arriving at the end of the line, the train pauses while the engine is switched to the other end for the return trip. You won't actually see the mine which is well away from the track. But there is plenty of action to observe as the crushed phosphate rock is being loaded into open rail cars.
Phosphate rock, also known as phosphorite, is mined for its phosphorus content. These resources occur principally as Eocene sedimentary marine deposits in the Gafsa basin where the phosphate beds are exposed on the flanks of elongated dome-like structures. Rocky overburden is removed forming open pit mines from which the phosphorite is removed. Up until about ten years ago, much of the ore was extracted by underground mining. But this is more expensive than removing the rock above the ore and simply scooping it up.
Calcium phosphate is the main chemical component in phosphorite. Fluoride, often present as an impurity, is removed during refining. Interestingly, the geologic process by which calcium phosphate is formed is not well understood. The prevailing theory suggests that calcium carbonate in certain limestone deposits is slowly converted to calcium phosphate by phosphorus dissolved from the surrounding rock.
The phosphate rock is crushed and transported by rail to processing plants where it is converted into various useful products for export. More than 85% of it is used for the production of fertilizer for agriculture. It is first reacted with sulfuric acid to produce phosphoric acid which is further reacted with phosphorite to produce the fertilizer triple superphosphate. The phosphoric acid may also be reacted with ammonia to make ammonium phosphate fertilizer. Phosphorus smelted from the ore is used to make a variety of industrial chemicals such as food preservatives, anti-corrosion agents, pesticides and water treatment chemicals.
When purified, phosphoric acid is used to produce a variety of products such as animal feed supplements. A familiar use of purified phosphoric acid is as a food ingredient. This is the chemical that gives Coca Cola, Pepsi and other sodas their characteristic bite taste. Not surprisingly, this highly acidic material has been linked to erosion of tooth enamel.
LOGGING THE CACHE
To log this cache, you must do the following:
1. Send me an e-mail with the answers to the following two questions.
What is the color of the ore loaded into the rail cars?
What is the name of the station/office at the end of the rail line? This is shown in a large sign over the door. NOTE: At last report the sign has been removed. If the sign is not there, tell me the two colors with which the building is painted.
2. You may post a picture of yourself (optional) with your GPS in front of the train station sign near the coordinates or in front of any mining or ore transportation operation.
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