Bauxite
Alumina
Corundum
An aluminum silicate
18. The passage supplies information for answering all of the following questions regarding aluminous minerals EXCEPT:
What percentage of the aluminum in the Earths crust is in the form of bauxite?
Are aluminum-bearing nonbauxite minerals plentiful?
Do the aluminous minerals found in bauxite contain hydrated oxides?
Are aluminous hydrated oxides found in rocks?
Do large quantities of bauxite exist?
19. The author implies that corundum would be used to produce aluminum if
corundum could be found that is not contaminated by silicates
the production of alumina could be eliminated as an intermediate step in manufacturing aluminum
many large deposits of very high quality corundum were to be discovered
new technologies were to make it possible to convert corundum to a silicate
manufacturers were to realize that the worlds supply of bauxite is not unlimited
Traditionally, the study of history has had fixed boundaries and focal pointsperiods, countries, dramatic events, and great leaders. It also has had clear and firm notions of scholarly procedure: how one inquires into a historical problem, how one presents and documents ones findings, what constitutes admissible and adequate proof.
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