Modularity of crystal structures: a unifying model for the biopyribole–palysepiole series
Abstract
Biopyriboles and palysepioles are two polysomatic series traditionally described as built by the juxtaposition of modules
taken, respectively, from phyllosilicates and pyroxenes and from palygorskite and sepiolite.We show that all the minerals in these two
series can be described in the framework of the tropochemical cell-twinning model as built by modules of variable width taken from
phyllosilicates, stacked by different structure-building operations. We present a quantitative comparison of the modules occurring in
the different minerals and show their structure is so closely similar that one can use the module taken from one mineral to model the
structure of the other minerals with only minimal deformations.