In geology, a pseudomorph is a mineral compound resulting from a substitution process in which the appearance and dimensions remain constant, but the mineral which makes up the chief component of the compound is replaced by another. The name literally means False Form. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... For other uses, see Mineral (disambiguation). ...

Three kinds of pseudomorph exist:

A paramorph (also called allomorph) is a mineral changed on the molecular level only. It has the same chemical composition, but with a different structure. The mineral looks identical to the original unaltered form. This occurs, as an example, in the aragonite to calcite change. Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ... Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ...

An infiltration pseudomorph is a pseudomorph in which one mineral or other material is replaced by another. The original shape of the mineral remains unchanged, but color, hardness, and other properties change to those of the replacing mineral. An example of this process (also called substitution) is the replacement of wood by silica (quartz or opal) to form petrified wood in which the substitution may be so perfect as to retain the original cellular structure of the wood. An example of mineral-to-mineral substitution is replacement of aragonite twin crystals by native copper, as occurs at Corococo, Bolivia. The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... For other uses, see Quartz (disambiguation). ... For other uses, see Opal (disambiguation). ... Petrified log at the Petrified Forest National Park A petrified tree from California Petrified wood is a type of fossil: it consists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate, such as quartz), while retaining the original structure of the wood. ... Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ... It has been suggested that twin boundary be merged into this article or section. ... Although copper most commonly occurs in oxidized states and mixed with other elements, it is found in its native form in various regions of the world. ...

A variety of infiltration or substitution pseudomorphism is called alteration, in which only partial replacement occurs. This happens typically when a mineral of one composition changes by chemical reaction to another of similar composition, retaining the original crystalline shape. An example is a change from galena, lead sulfide, to anglesite, lead sulfate. The resulting pseudomorph may contain an unaltered core of galena surrounded by anglesite that has the cubic crystal shape of galena. For other uses, see Galena (disambiguation). ... Anglesite specimen in its orthorhombic crystalline form Anglesite is a lead sulfate mineral, PbSO4. ...

An incrustation pseudomorph results from a process by which a mineral is coated by another and the encased mineral dissolves. The encasing mineral remains intact, and retains the shape of the original mineral or material. Alternatively, another mineral may fill the space (the mold) previously occupied by some other mineral or material.

Pseudomorphs are also common in paleontology. Fossils are often formed by pseudomorphic replacement of the remains by mineral matter. Examples would include petrified wood and pyritized gastropod shells. Paleontology, palaeontology or palæontology (from Greek: paleo, ancient; ontos, being; and logos, knowledge) is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. ... For other uses, see Fossil (disambiguation). ... Petrified log at the Petrified Forest National Park A petrified tree from California Petrified wood is a type of fossil: it consists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate, such as quartz), while retaining the original structure of the wood. ... The mineral pyrite, or iron pyrite, is iron sulfide, FeS2. ... Subclass Subclass Eogastropoda     Patellogastropoda Subclass Orthogastropoda   Superorder Cocculiniformia   Superorder Hot Vent Taxa     Neomphaolida   Superorder Vetigastropoda   Superorder Neritaemorphi     Neritopsina   Superorder Caenogastropoda     Architaenioglossa     Sorbeoconcha   Superorder Heterobranchia     Heterostropha     Opisthobranchia     Pulmonata The gastropods, or univalves, are the largest and most successful class of mollusks, with 60,000-75,000 species, and second largest class...

Terminology for pseudomophs is "replacer after original", as in brookite after rutile.

References

• Dana's Manual of Mineralogy by Cornelis S. Hurlbut, Eighteenth Edition, (1971, John Wiley & Sons, Inc.) ISBN 0-471-42225-8