Pseudomorphs

If a crystal changes chemically or structurally, yet keeps the shape of the original, it is called a pseudomorph or "false form"; it looks like a crystal of one species but is composed of another (Sinkankas). Pseudomorphs include the following:

Paramorphs are the result of polymorphism, the existence of a chemical compound or element in two or more crystal structures (KL).

Alteration pseudomorphs result from processes involving chemical reactions (KL).

Replacement pseudomorphs involve complete or partial solution and chemical precipitation of a new substance (KL).

Epimorphs occur where an original mineral is encrusted by a second one, but the core of the first mineral remains unchanged (KL).

Perimorphs occur where an original mineral is encrusted by a second and then the first mineral is leached away leaving a hollow shell in the form of the original mineral (KL).

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