Pseudomorph
mineral or mineral compound that appears in an atypical form
In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another due to alteration, or chemical substitution, dissolution and refilling, structural changes or incrustation. The name literally means "false form". Terminology for pseudomorphs is "replacer after original", as in brookite after rutile. The term pseudomorphoses was initially used by Haüy.
Substitution pseudomorph
A substitution pseudomorph is a pseudomorph in which one mineral or other material is replaced by another. The original shape of the mineral remains unchanged, but chemical composition, color, hardness, and other properties change to those of the replacing mineral.
This happens typically when a mineral of one composition changes by chemical reaction to another of similar composition, retaining the original crystalline shape. It can occur due to the loss of water or through the action of atmospheric agents, such as oxidation, hydration, or carbonation. An example is a change from galena (lead sulfide) to anglesite (lead sulfate) by oxidation. Pyrite crystals transformed into limonite, a compact mixture of iron oxides where goethite generally predominates, are common.
The public source identifies “Pseudomorph” as mineral or mineral compound that appears in an atypical form. This brief keeps that definition visible, then builds a research path around Pseudomorph, mineral and compound.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Aug 19, 2025. The linked authority identifier is Q1456639. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Pseudomorph” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.