“…The rationale of course is that they occur as lavas and minor intrusions and exhibit such igneous features as chilled contacts, pillows, autobrecciation, perlitic cracks indicating devitrification of glass, phenocrysts, and matrix textures. This conclusion is presented concisely by Amstutz (1968) who categorically states 'If the fabric relations are considered, it is evident that many spilites and keratophyres must be primary, because no secondary diffusion process is able to mimetically reproduce a primary process'.…”