Definition of phyllosilicate
: a mineral of a class of polymeric silicates in which the silicon-oxygen tetrahedral groups are linked by sharing three of every four oxygen atoms so as to form sheets of indefinite extent, in which the ratio of silicon to oxygen is 2:5, and in which some silicon atoms may be replaced by aluminum (as in mica, chlorite, kaolinite) — called also
sheet-silicate; compare cyclosilicate, inosilicate, nesosilicate, sorosilicate, tectosilicate
