Biopyriboles and polysomatic series 论文

摘要

Many crystals may be regarded as made of layer modules that are chemically distinct and that in different crystals may occur in different pioportions, giving rise to polysomatic series. The humites constitute a classic example, as do certain phyllosilicates and hydroxides. Amphiboles, in particular,_ may be factored by (010) cuts inio layers that are alternately pyroxene and trioctahedral mica (or talc). The pyroxenes, amphiboles, and trioctahedral micas thus form several such series and we shall designate these minerals, collectively, as the biopyriboles, following Johannsen (l9ll). Each such series shows interesting relationships connecting the unit cells and space groups of successive members. The existence of these series also leads to useful chemographic relations in composition space.