Allomorph

1. n. A variety of pseudomorph which has undergone partial or complete change or substitution of material; — thus limonite is frequently an allomorph after pyrite.
2. n. 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.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.