Industrial deposits of boron are usually produced by chemical precipitation. Precipitation occurs
following concentration on land, in brine waters in arid regions or as terrestrial evaporites and arid
playa deposits (56)
. Precipitation also occurs as marine evaporites after concentration due to evaporation
of seawater. Borates also form in salt domes and by further concentration of underground
water in arid areas (56)
. The borate deposits of economic importance are restricted to arid areas
because of the high solubility of these minerals.
Hydrated borates are formed originally as chemical deposits in saline lakes (57)
. The particular
mineral suite formed is dependent on the chemical composition of the lake. Two kinds of borate
deposits are formed in the arid western United States (57)
. Hydrated sodium borates form from
lakes that have a high pH and that are high in sodium and low in calcium content. Hydrated
sodium-calcium borates form from lakes of higher calcium content.