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The most important Permian economic deposits are rock salt and potash salts,
coal, oil, and gas. Economically important evaporites (salts formed by chemical
precipitation under generally arid conditions) of Permian age are found in the ...
Principal types of phosphate deposits. Mineral deposits of phosphate are of six
principal types, listed in approximate order of size and world importance: (1)
marine phosphorites; (2) igneous apatite deposits; (3) residual phosphorites; ...
The hard-rock phosphate deposits of northwestern peninsular Florida are
phosphatized limestone fragments and plates in the Ala- chua Formation of
Pliocene age. These deposits are small, but some contain as much as 35 percent
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The New Encyclopaedia Britannica (Encyclopaedia)User Review - Not Available - Book Verdict
For virtually all its 238 years,Britannica has ruled the shelves as a peerless general encyclopedia. Reviewers have consistently given it high marks for most of the 12 criteria identified inKister's ... Read full review