Unit 8 - Industrial Minerals Flashcards
In plant nutrition, what is required for plants to absorb nutrients from the soil?
Plant nutrients must be in a water-soluble form so that the plants can obtain them from the soil water they extract through their roots.
What factors led to the decline of the Chilean guano trade?
Between 1878 and 1885, nitrate compounds from the Atacama Desert and phosphates from evaporates in France and today’s Germany replaced natural guano in the fertilizer trade.
What is the trend in the ratio of fertilizer application to grain production? What are the implications of this trend?
Since the early 1960s, there have been diminishing returns from the use of fertilizer on grain crops. This might imply that using chemical fertilizers, which do not remain in the soil from year to year, depletes the soil of other important nutrients that would accrue from using manure.
Why are natural nitrate mineral deposits scarce? How do they form?
Because nearly all nitrate compounds are extremely soluble, they are commonly washed away by precipitation and ground water. Where they do occur, they form a crust caused by the oxidation of nitrogen-bearing substances in the presence of other salts.
Describe how sodium nitrite forms in the Atacama Desert of Chile.
The Atacama Desert of Chile has the reputation of being the driest place on Earth. Fogs are common there, however, and the tiny fog droplets contain mineral salts blown into the air from the evaporation of sea spray. When the fog precipitates on the desert floor, the minerals remain in the soil. The sodium nitrates are dissolved by infrequent rains and left as a cement or caliche that can be extracted from the soil.
Describe the principle behind the Haber-Bosch process for producing ammonia used in fertilizers.
In the Haber-Bosch process, controlled combustion of a fossil fuel (usually natural gas) yields carbon monoxide and hydrogen. Atmospheric nitrogen, assisted by a catalyst, will react with the hydrogen to form ammonia, which can be used as a component in fertilizers.
About seventy-five per cent of the world production of nitrogen is used for fertilizers. What are the other uses for nitrogen?
Although about seventy-five percent of world nitrogen is used for fertilizers, nitrogen is used in the production of plastics, fibres, resins, refrigerants, detonating agents for explosives, and nitric acid.
What are the three main sources of phosphate?
Phosphate (P2O5, the oxide of phosphorus) is present in the mineral apatite, in guano deposits, and in bones.
What is superphosphate?
Superphosphate is a form of phosphorus more soluble than phosphate. It is formed by dissolving bone in sulphuric acid.
Which country produces the largest amount of phosphorus? What environmental concerns emerge from mining phosphate?
The United States is the world’s largest producer of phosphate, having large deposits in North Carolina, Florida, Tennessee, and five contiguous states in the west. The phosphate deposits are relatively thin and near the surface, making mining by draglines and dredges very efficient. There are increasing environmental concerns, however, because large amounts of water must be pumped out of the mines, trace amounts of radioactive elements are released in the mining process, and very large mounds of fine-grained gypsum are created as a result of sulphuric acid treatment.
Briefly describe the most recently discovered source of phosphate in the United States, and discuss its potential.
The USGS has recently found phosphate crusts and nodules on the continental shelf off the coast of Florida. Although the deposits are of lower grade than their continental counterparts, they are vast in size.
Why is potassium especially important to plants?
Nitrogen and phosphorus are integral parts of plant cells and crucial to plant metabolism. Potassium, on the other hand, is an important catalyst in nitrogen metabolism, synthesis of proteins, and activation of enzymes in plants. Potassium also assists in maintaining water balance.
How do commercially viable potassium deposits occur?
The commercially viable potassium deposits that can be used for fertilizer occur as evaporite deposits. They are found today in arid and semi-arid areas where percolating groundwaters haven’t dissolved and removed the potassium.
Where is the western world’s largest supply of potassium located?
The province of Saskatchewan, in Canada, has the world’s largest potassium reserves, and is the second largest producer behind the Perm region of Russia.
In what forms does sulphur occur on Earth’s surface?
Sulphur occurs at the Earth’s surface as native metal, as metal sulphides, as mineral sulphates dissolved in oceans, as hydrogen sulphide in natural gas (Alberta is the world’s largest producer of this form), and as organic sulphur in hydrocarbons such as coal and petroleum.
Briefly account for the occurrence of sulphur in association with salt domes.
Gypsum and anhydrite often occur as a cap on salt domes. When they are brought near the surface by expanding salt, they are attacked by anaerobic bacteria, which extract the oxygen and convert the gypsum into calcite and free sulphur. The same bacterial action and production of free sulphur can result from groundwater percolating through voids in gypsum beds associated with sequential evaporite deposits.
Describe the Frasch process for extracting sulphur.
The Frasch process uses a three-pipe configuration, one inside the next, placed in a twenty-five centimetre hole that is drilled into sulphur-bearing rock. Hot water (140 °C) pumped down the outer pipe melts the sulphur. The inner pipe is used to force air into the mixture, driving it into and through the middle pipe up to the surface.
What are the uses of the sulphur produced today?
A large amount of sulphur (eighty per cent of US production) is used to manufacture sulphuric acid. Sulphur and sulphuric acid are used in the production of soaps, rubber, bleaches for the pulp industry, plastics, acetate, cellophane, rayon, explosives, and leachates. Sulphur is also used as a pickling agent for steel.
Describe the stages of mineral precipitation during the evaporation of sea water.
As sea water begins to evaporate, calcium carbonate (CaCO3) begins to crystallize and settle to the bottom in small amounts. When the original volume of sea water has been reduced to nineteen per cent, anhydrite (CaSO4) or gypsum (CaSO4·2H2O) begins to precipitate. The greatest amount of precipitate is accounted for by halite (NaCl), which begins to crystallize when the original volume of sea water is reduced to 9.5 per cent. At four per cent, potassium salt (KCl) and the magnesium salts (MgCl2 and MgSO4) crystallize.
The evaporation of a body of sea water the size of the Mediterranean would yield layers of halite and gypsum only twenty-four and 1.4 metres thick, respectively. How, then, can we account for beds of these minerals up to 1000 metres thick in the fossil record?
Thick beds of halite and gypsum can be explained only by the continuous evaporation of sea water in a partially isolated basin that was episodically renewed over a period of thousands of years. The original body of sea water must have been reduced to a small volume by evaporation, resulting in a layer of salts on the bottom, after which sea level rose and water flowed into the basin, repeating the cycle. This process must have occurred many times.
Where are present-day evaporite basins located, and why is the Mediterranean Sea not considered one of them?
Currently, there are no evaporite basins as large as those that existed in the geologic past. Evaporite basins do occur, however, at the eastern edge of the Caspian Sea, the Red Sea, the Great Salt Lake in Utah, and the Dead Sea. Mineral salts do precipitate and settle to the bottom in the Mediterranean Sea, but the bottom current that flows westward through the Strait of Gibraltar removes these brines to the Atlantic.
How do near-surface salt domes form?
Many salt beds are located too deep to mine, but in some areas, notably in coastal areas of the Gulf of Mexico, the salt has risen in great columns as salt domes. These domes develop because the salt is less dense than the overlying rocks so the salt rises buoyantly toward the surface if the overlying rock layers or sediment deposits are weak enough.
What are the major uses of salt produced today?
About sixty per cent of salt produced is used in the chemical industry for the manufacture of chlorine gas and sodium hydroxide. Approximately fifteen per cent is used for de-icing, and less than six per cent is used as table salt.
What are sodium carbonate (soda ash) and sodium sulphate (salt cake) used for?
Sodium carbonate and sodium sulphate are widely used in water treatment and in the manufacture of glass, soaps, dyes, detergents, insecticides, and paper.
How do these mineral deposits form, and where are they located today?
Sodium carbonate and sodium sulphate are evaporite minerals that form in lakes of arid regions where the weathering of rocks releases sodium and/or sulphur. Although most of the current production comes from lakes from the geologic past, some present-day examples of such lakes would be the Searles, Owens, and Mono Lakes of California, the Great Salt Lake of Utah, and Lake Magadi in Kenya.
