Chapter 3 - Calcium, Magnesium, or Silicate Buried Deposits

Abstract

This chapter presents a discussion on calcium, magnesium, or silicate buried deposits in various countries of the world. The Sijes district has four major borate mining areas: Monte Amarillo, Monte Verde, Esperanza, and Santa Rosa in Argentina. The borates occur in many forms: massive, nodular, lenticular, interlayered, and disseminated. There are 55 underground and open pit mines in 112 separate borate deposits in the Liaoning area of the Liaodong Peninsula in northeastern China. In California, 23 borate deposits in the Death Valley region in Black Mountain are found. The borate zone consists of clays, tuffaceous mudstone, shale, sandstone, zones of tuff, limestone and basalt, and borates interbedded within these rocks. Borosilicate occurrences have been reported in an area of volcanic and ultrabasic rocks in Albania. A very large number of borates occur where they are considered to be low-grade deposits or as a minor component of other rocks or deposits. Many metallic ore deposits contain borates such as the tin borates in northwestern Tasmania, with economic amounts of B, Cu, Zn, W, and Be. The most common borate is from the family of tourmalines. Another common boron-containing mineral is substituted potassium feldspar. Boron may also replace the aluminum in albite. Clays settled in seawater adsorb considerable boron, particularly illite.