Allofonit

Allofonit is a fictional mineral that appears in speculative geology and science fiction narratives. It is used in educational contexts to illustrate crystallography, mineral classification, and the behavior of silicate frameworks under extreme conditions. Although not observed in nature, Allofonit is described across multiple sources as a framework silicate with a three-dimensional tetrahedral network.

In the fictional description, the mineral hosts a variable composition dominated by silicon and oxygen, with a cationic sublattice that can include magnesium, iron, calcium, or rare earth elements. The structural class is typically placed among tectosilicates, with channels or cages that could accommodate hydrous or volatile components in some versions of the model.

Commonly cited physical properties in these accounts include a Mohs hardness of about 6 to 7, a vitreous to pearly luster, and a pale to mid-gray color with possible greenish tints. Density is described as roughly 2.8 to 3.3 g/cm3, and crystal habit ranges from prismatic to blocky forms. Many narratives attribute distinctive optical properties, such as moderate birefringence, to the mineral.

Allofonit is said to form in high-temperature, high-pressure environments, such as deep crustal subduction zones, or during hydrothermal alteration in fictional settings. In some contexts it is depicted as synthesizable in laboratory conditions given intense pressure and specific chemical environments.

See also: List of fictional minerals, crystallography in fiction, mineralogy in literature.