The Elements of economic geology

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Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

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Document type:: Monograph

Structure type:: Chapter

Title:: Part III. Earthy minerals

Collection:: Economics Books

216 ECONOMIC GEOLOGY sodium), langbeinite (double sulphate of magnesium and potassium); and with the triple sulphate polyhalite (sulphate of calcium, magnesium, and potassium with two molecules of water). After the sulphates follows the precipitation of the chlorides, such as sylvite (KCl) which may be combined with magnesium chloride, as carnallite (KCl, MgCl, 6H,0), or as hartsalz, a mixture of sylvite, rock-salt, and kieserite. Intermediate between the sulphates and the chlorides is kainite—sulphate of magnesia combined with chloride of potassium and water (MgSO,, KCl, 3H,0). These minerals may be formed by the complete evaporation of an inland sea, of which the waters have remained nearly saturated for a long time. SeconpaRY CoNCENTRATIONS—Potash salts, owing to their extreme solubility, are less abundant than rock-salt ; for the potash is less often deposited, and more likely to be removed in solution. The largest supply of known potash salts is in Central Germany, where, as explained on page 209, the bittern was occasionally evaporated and beds of primary potash laid down. Even there, however, owing to the solu- bility of the potash salts many of the beds of commercial importance are secondary, and have been redeposited. The upturned edges of a series of beds of rock-salt, carnallitite {i.e. impure carnallite), and kieserite is covered by a sheet of kainite which occasionally projects into the underlying beds. This kainite is of secondary origin for it is traversed by the upward continuation of layers of rock-salt which have re- sisted solution ; whereas the carnallite and kieserite, owing to their greater solubility, have been replaced by kainite. At the Hercynia Mine near Vienenburg, rock-salf, hauptsalz (a mixture of carnallite, rock-salt, and kieserite), anhydrite, carnallitite, and sylvinite (i.e. KCl NaCl), are capped by secondary deposits of sylvinite and kainite} which have not also replaced the rock-salt or anhydrite. The secondary origin of the sylvinite is further proved at the Ronenberg Mine, as a fault has displaced the rock-salt and anhydrite, but not the sylvinite, which occurs along and across the fault plane. These secondary potash deposits like the German salt domes were due to the percolation of water along fractures contemporary with the uplift of the Alps.

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