Vermiculite refers to a mineral group and an industrial commodity (see part A for a description of both) and a mineral species. As a mineral species, the basic structure is a 2:1 layer [ideally Mg₃(Si₃Al)O₁₀] regularly interstratified with a partially completed interlayer [Mg_0.5(H₂O)₄], thus with an overall composition of Mg₃(Si₃Al)O₁₀ ^. Mg_0.5(H₂O)₄ in either space group Cc or C2/c. Vermiculites are generally alteration products of (trioctahedral) mica or chlorite and form in soils, with most vermiculite species being trioctahedral, although fine-grained soil varieties may be either dioctahedral or trioctahedral. The 2:1 layer has a net layer charge of -0.6 to -0.9 per formula unit, which is offset by the interlayer to achieve overall neutrality. Like smectite minerals, vermiculite has swelling capabilities. Stacking sequences depend on the H₂O and cation configurations of the interlayer.
See intumescence in Part 1 of the Glossary.

Vernadite, MnO₂ ^. H₂O, is poorly crystalline and not well studied (Post, 1999). It is a mixture of nano-plates of birnessite, buserite, and interstratified birnessite / buserite. Vernadite occurs in the oxidized zone of Mn ore deposits, as buried manganese nodules on the sea floor, and ferromanganese crusts on seamounts. In soils (Chukhrov et al., 1980), vernadite is believed to be related to microbial oxidation of Mn²⁺.

An obsolete term for celadonite.

An obsolete term for celadonite.

A method of measuring intramolecular or intracrystalline modes of motion (vibrational modes) by observing the interaction of incident radiation with a sample. Common techniques used to obtain spectra are infrared and Raman spectroscopy, and inelastic neutron scattering.
Cf., spectroscopy, normal mode

The measured hardness of a surface as tested using a special diamond pyramid-shaped indenter under various loads. A Vickers number is reported based on surface area indented (in mm²) divided by pressure (in Newtons).
Cf., hardness, Mohs hardness

A general term used in the pelotherapy clay industry to denote an unmodified (“raw”) clay from a deposit, before maturation with saline or mineral water.

An obsolete term for an iron-rich chlorite.

A measure of the resistance of a fluid to flow when the fluid is placed under stress.

An obsolete term for a mixture of allophane and wavellite from Santa Rosa de Viterbo, Colombia.