Chapter 11: Problem 1
Which of the following is not an ore of aluminium? (a) Bauxite (b) Cryolite (c) Kernite (d) Corundum
Short Answer
Expert verified
Kernite (c) is not an ore of aluminium.
Step by step solution
01
Understanding the concept of an ore
An ore is a natural occurrence of rock or sediment which contains enough minerals with economically important elements, typically metals, that can be extracted from the deposit economically. The ores are extracted through mining; these are then refined to extract the valuable elements.
02
Identifying aluminum ores
The most commonly known aluminum ore is bauxite. Other ores that contain aluminum include cryolite and corundum. These minerals contain aluminum in a form that can be economically extracted.
03
Recognizing the non-aluminum ore
Kernite is not an ore of aluminum. Kernite is an ore of boron, therefore, it does not contain aluminum in an economically extractable form.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ore Definition
Understanding what constitutes an ore is a fundamental concept in the field of geology and mining engineering. An ore is a type of rock that contains minerals with important elements including metals that can be extracted from it at a profit.
When we say that a rock is an ore, we imply that the concentration of the metal within it is high enough that mining the rock and processing it yields a valuable amount of metal. Not every rock with a trace of metal qualifies as an ore; it's about the metal's abundance and the feasibility of its extraction.
Thus, the economic viability is the key aspect of an ore. This viability is often dependent on the market price of the metal, the cost of extraction, and the presence of a market for the material.
When we say that a rock is an ore, we imply that the concentration of the metal within it is high enough that mining the rock and processing it yields a valuable amount of metal. Not every rock with a trace of metal qualifies as an ore; it's about the metal's abundance and the feasibility of its extraction.
Thus, the economic viability is the key aspect of an ore. This viability is often dependent on the market price of the metal, the cost of extraction, and the presence of a market for the material.
Bauxite
Bauxite is one of the primary ores of aluminium and is indeed the most abundant. It is a heterogeneous material, generally consisting of one or more aluminium hydroxide minerals, including gibbsite, boehmite, and diaspore.
To envision where bauxite comes from and why it's so valuable, think about how aluminium, a metal that's both lightweight and strong, plays a critical role in a myriad of applications, from aerospace to kitchen foil. Bauxite forms in tropical and subtropical environments where warm temperatures allow for intense weathering of surface rocks, leading to the concentration of aluminium oxides which are then mined.
What's remarkable is that from bauxite, through a process known as the Bayer process where impurities are removed, we obtain alumina (aluminium oxide) which is then used in the Hall-Héroult process to produce aluminium metal.
To envision where bauxite comes from and why it's so valuable, think about how aluminium, a metal that's both lightweight and strong, plays a critical role in a myriad of applications, from aerospace to kitchen foil. Bauxite forms in tropical and subtropical environments where warm temperatures allow for intense weathering of surface rocks, leading to the concentration of aluminium oxides which are then mined.
What's remarkable is that from bauxite, through a process known as the Bayer process where impurities are removed, we obtain alumina (aluminium oxide) which is then used in the Hall-Héroult process to produce aluminium metal.
Cryolite
Cryolite is another aluminium ore, although less well-known compared to bauxite. Its significance stems from its use in the Hall-Héroult process, as a solvent for alumina, without which pure aluminium metal cannot be economically produced.
Cryolite is a fluoride mineral composed of sodium, aluminium, and fluoride (Na3AlF6). This mineral was historically mined in large quantities in Greenland, but now it is mostly synthesized for industrial use. It lowers the melting point of alumina and serves as a medium to dissolve it, allowing for a more efficient extraction of aluminium. Therefore, while not used as a direct source of aluminium like bauxite, cryolite plays an indispensable role in the production of aluminium metal which illustrates the diverse nature of 'ores' in metallurgical processes.
Cryolite is a fluoride mineral composed of sodium, aluminium, and fluoride (Na3AlF6). This mineral was historically mined in large quantities in Greenland, but now it is mostly synthesized for industrial use. It lowers the melting point of alumina and serves as a medium to dissolve it, allowing for a more efficient extraction of aluminium. Therefore, while not used as a direct source of aluminium like bauxite, cryolite plays an indispensable role in the production of aluminium metal which illustrates the diverse nature of 'ores' in metallurgical processes.
Corundum
Lastly, corundum is an aluminium-based mineral known for its hardness, second only to diamond. This mineral existing as transparent crystals can be gemstones like rubies and sapphires, but when opaque, it is used as an abrasive.
Corundum's formula is Al2O3, the same as alumina, which we obtained from processing bauxite. Although corundum contains a high concentration of aluminium and is chemically similar to alumina, it's not typically processed for aluminium extraction due to its cost and use as a gemstone or abrasive. Its economic value in other applications typically outstrips its value as an aluminium ore.
Understanding these different forms of aluminium ores illuminates the interplay between a mineral's composition, its extraction feasibility, and its market demand—key considerations that determine whether a mineral counts as an ore of a particular metal. Corundum, while an aluminium mineral, is predominantly valued for other properties and uses.
Corundum's formula is Al2O3, the same as alumina, which we obtained from processing bauxite. Although corundum contains a high concentration of aluminium and is chemically similar to alumina, it's not typically processed for aluminium extraction due to its cost and use as a gemstone or abrasive. Its economic value in other applications typically outstrips its value as an aluminium ore.
Understanding these different forms of aluminium ores illuminates the interplay between a mineral's composition, its extraction feasibility, and its market demand—key considerations that determine whether a mineral counts as an ore of a particular metal. Corundum, while an aluminium mineral, is predominantly valued for other properties and uses.
