Copper pyrites (copper), galena (lead), blende (zinc), cinnabar (mercury), &c. Of the sulphates we notice gypsum and anhydrite (calcium), barytes (barium) and kieserite (magnesium).
These deposits, in addition to common salt, include the following minerals: sylvine, KC1; carnallite, KC1 MgC12.6H20 (transparent, deliquescent crystals, often red with diffused oxide of iron); kainite, K 2 SO 4 MgSO 4 MgC1 2 6H 2 O (hard crystalline masses, permanent in the air); kieserite MgS04 H20 (only very slowly dissolved by water); besides polyhalite, MgSO 4 K 2 SO 4.2CaSO 4.2H20anhydrite, CaSO 4; salt, NaC1, and some minor components.
For the purpose of the manufacturer of this salt these are assorted into a raw material containing approximately, in Ioo parts, 55-65 of carnallite (representing 16 parts of potassium chloride), 20-25 of common salt, 15-20 of kieserite; 2-4 of tachhydrite (CaC12 2MgC12 12H20), and minor components.
The undissolved residue produced in either process consists chiefly of kieserite and common salt.
Magnesium is found widely distributed in nature, chiefly in the forms of silicate, carbonate and chloride, and occurring in the minerals olivine, hornblende, talc, asbestos, meerschaum, augite, dolomite, magnesite, carnallite, kieserite and kainite.
In thickness of carnallite, MgC1 2 KC1.6H 2 O, mixed with a little salt; this is followed by a thicker deposit of kieserite, MgSO 4 H 2 O, containing rather more salt than the upper bed.