What does allomorph mean?
The definition of allomorph
Etym: [Gr. (Min.)
(a) Any one of two or more distinct crystalline forms of the same substance; or the substance having such forms; — as, carbonate of lime occurs in the allomorphs calcite and aragonite.
(b) A variety of pseudomorph which has undergone partial or complete change or substitution of material; — thus limonite is frequently an allomorph after pyrite. G. H. Williams.