petschite — variety from marialite-meionite series; see petschite in ‘Classification’ …
phenakite — species of mineral; see phenakite in ‘Classification’ …
phonolite — a rare extrusive igneous rock, of intermediate chemical composition between felsic and mafic …
phosphophyllite — species of mineral; data; faceted specimens exist …
phosphosiderite — species of mineral; see phosphosiderite in ‘Classification’ …
pleochroism — оn optical phenomenon in which the gemstone appears to be different colours when observed at different angles …
pleonaste — variety of spinel; see pleonaste in ‘Classification’ …
pneumatolysis — the alteration of rock or mineral crystallisation effected by gaseous emanations from solidifying magma …
pollucite — species of mineral; see pollucite in ‘Classification’ …
poudretteite — species of mineral; data; faceted specimens exist …
povondraite — species of mineral; data; faceted specimens exist …
powellite — species of mineral; data; faceted specimens exist …
prasiolite — variety of quartz; see prasiolite in ‘Classification’ …
prehnite — species of mineral; see prehnite in ‘Classification’ …
prismatine — species of mineral; faceted specimens exist …
psilomelane — obsolete name; see psilomelane in ‘Classification’ …
pyrite — species of mineral; data; faceted specimens exist …
pyroclastics — clastic rocks composed solely or primarily of volcanic materials …
pyrope — species of mineral; see pyrope in ‘Classification’ …
pyrope-almandine series — a series between pyrope and almandine; see pyrope-almandine series in ‘Classification’ …
