Pseudominerals

Pseudominerals is an informal label used to describe natural solids that resemble minerals but do not meet the formal criteria for minerals. In mineralogical terms, a mineral is a naturally occurring, inorganic solid with a definite chemical composition and an ordered crystalline structure. Pseudominerals typically fail one or more of these criteria, most commonly because they lack long-range crystalline order (they are amorphous) or because their composition does not form a true crystal lattice. As a result, many such materials are classified as mineraloids rather than minerals.

Common examples cited in field guides and educational sources include opal and obsidian. Opal is a hydrated, amorphous form of silica, while obsidian is volcanic glass with no crystalline structure. Other naturally occurring amorphous solids may be mentioned in popular discussions as pseudominerals. In formal mineralogy, however, the term is not widely used; such materials are typically described as mineraloids or simply as amorphous solids.

Identification and classification rely on assessing crystallinity and composition. Techniques such as X-ray diffraction determine whether a material is crystalline, while chemical analysis and optical or microscopic examination help distinguish true minerals from mineraloids. The distinction is important for accurate taxonomy, geologic interpretation, and applications in gemology and mineral collecting.

Pseudominerals thus illustrate the boundary between minerals and mineraloids and highlight the role of crystallinity in mineral classification. The term remains more common in nontechnical or historical contexts than in modern, formal mineralogical literature.