Delineation of Structural Defects in Natural Quartz by Selective Etching

Abstract

Etch pits along a linear low angle grain boundary, etch pits on intersecting low angle boundaries (with three and four branches), pile-up of dislocation etch pits, series of oriented etch pits along and differently oriented etch pits (at 60° and 180°) on either side of twin boundaries observed on habit prism faces are illustrated and described. Continuation of a linear low angle grain boundary from a habit prism face to a fractured prism surface of the same crystal is established. Correspondence of isolated etch pits, of non-intersecting and intersecting low angle grain boundaries and also of etch pits within and outside such twin boundaries on the two match fractured prism surfaces is established. Similar correspondence is shown for etch pits on match fractured prism surface when one of them is etched in KOH and the other in NaOH. Series of etch pits along the twin boundaries are attributed to dislocations. Rows of etch pits parallel to r-m edge observed on habit rhombohedral face and also on fractured prism surface are illustrated and interpreted. Alignment of etch pits perpendicular to r-m edge is attributed to polygonization.