Hornblende asbestos

Silicon makes up 25.7% of the earth s crust, by weight, and is the second most abundant element, being exceeded only by oxygen. Silicon is not found free in nature, but occurs chiefly as the oxide and as silicates. Sand, quartz, rock crystal, amethyst, agate, flint, jasper, and opal are some of the forms in which the oxide appears. Granite, hornblende, asbestos, feldspar, clay, mica, etc. are but a few of the numerous silicate minerals. 

Hornblende-asbestos Obsolete synonym of amphibole asbestos. The term is derived from the early use of hornblende for the group of minerals now called amphiboles. Hornblende, defined today as a mineral series within the amphibole group, rarely occurs in fibrous form. 

Hornblendes, one series of Ca—Al-containing amphiboles (see Table 2.4), are particularly common minerals. Their chemical and physical properties resemble those of the tremolite-actinolite series, but hornblendes generally do not occur in a fibrous habit. They contain Al" in both tetrahedral and octahedral sites, whereas the asbestos varieties of amphibole contain little Al. This observation suggests that small variations in composition may be one of the important factors in generation of fibrous amphiboles. 

Other related cell (rat tumor and lung cells)/silicate (Chrysotile-sheet silicate asbestos, silicon, silica, hornblende) interaction studies performed using ESCA have been reviewed in detail elsewhere by Seal and his coworkers [177-180]. The general feature inherent to all of these systems is that there seems to be a particular type of chemical interaction between the cells and the silicate involving direct coupling between the cell and the tetrahedral silicate subunit with a corresponding release of these components to the octahedral subunit (i.e., the Al, Mg, and particularly the Fe). The results also suggest that some of the Fe is inserted into the cell. 

The minerals in the amphibole group are of this type. Different substitutions may make the formulas very complicated and sometimes formally deviating from 0/Si=2.75. Specific mineral examples are hornblende NaCa2(Mg,Fe),3Al3Sig022 (OH)2 (Figure M61) and actinolite (asbestos of amphibole type) Ca2(Mg,Fe)5(OH (Figure M62). 

---