A modulated 2:1 layer silicate with a continuous octahedral sheet and a tetrahedral sheet that involves triple chain strips linked by pairs of inverted tetrahedra that connect the strips and adjacent layers (Eggleton and Guggenheim, 1986). The ganophyllite chemical composition is approximately (K,Na,Ca)₆(Mg,Fe,Mn)₂₄(Si_32.5Al_7.5)O₉₆(OH)₁₆. 21H₂O. The large cations (K, Na, Ca) are exchangeable and occur associated near the undersaturated inverted tetrahedra that connect adjacent layers. Eggletonite is the Na analogue of ganophyllite. Ganophyllite occurs in low-grade metamorphic, silicate-rich manganese deposits, such as those found at the Harstig mine, Pajsberg, near Persberg, Vermland, Sweden.

A dioctahedral member of the true/brittle mica group with the ideal chemical composition of [Ba_0.5(Na,K)_0.5]Al₂(Si_2.5Al_1.5O₁₀(OH)₂. Ganterite may be described as a Ba- dominant analogue of muscovite-2M₁ that crystallizes, like most muscovite crystals, in space group C2/c. Ganterite was originally described from basement rocks of the Berisal Complex, Simplon Region, Switzerland (Graeser et al., 2003). but it has also been found from Oreana, Nevada, and Ba-rich muscovite-like phases have been reported from West Greenland; Ontario, Canada; and Franklin/Sterling Hill, New Jersey, USA.

A group of orthosilicate (= nesosilicate) minerals with stoichiometry of A₃B₂(SiO₄)₃, where divalent cations occur in the large-size (8-coordinated) A site and trivalent cations occur in the medium-size (6-coordinated octahedron) B site. Common garnet minerals are pyrope [Mg₃Al₂(SiO₄)₃], almandine [Fe₃Al₂(SiO₄)₃], spessartine [Mn₃Al₂(SiO₄)₃], uvarovite [Ca₃Cr₂(SiO₄)₃], grossular [Ca₃Al₂(SiO₄)₃], and andradite [Ca₃Fe₂(SiO₄)₃]. These garnets are separated into two series, pyralspite (the Mg, Fe, and Mn Al-rich members) and ugrandite (the Ca-rich members). Solid solution is common in the A site of pyralspite and in the B site of ugrandite, but little substitution between the two series. Grandite is a generic name for the grossular-andradite series. Garnet minerals commonly occur in metamorphic rocks, and are believed to be stable in the lower mantle of the earth. The minerals are generally cubic (= isometric) in symmetry. Garnet minerals are generally hard (Mohs hardness H: 6.5 to 7.5) and dense (specific gravity G: 3.5 to 4.5) and are used commercially as an abrasive.
Syn., silicate garnet

Although not a valid mineral name, garnierite is often used as a field term for nickel-bearing (± magnesium) hydrous phyllosilicates.

A small mineral concretion in the stomach. Some gastroliths may form if excess (ingested) clay cannot be eliminated by the digestive system. Some species, such as birds, reptiles, or dinosaurs, swallow small stones (gastroliths) that are believed to aid in digestion. These gastroliths are generally not concretions and are rounded and polished owing to the abrasive action within the stomach.

An obsolete term for a variety of talc that apparently deviates from the (OH) content of talc as determined in old literature, from Gava valley, Italy.

A measure of the ability of a colloidal system (i.e., a gel or sol) to withstand a load (shear force) without loss of the high slurry viscosity and/or the mechanical elasticity, often measured with a rheometer and expressed in units of mass per area. The gel strength is a function of the inter-particle forces present in the solid-liquid system.
Cf., colloid, suspension, gel, sol

An industrial term for clay minerals (especially palygorskite, sepiolite, Na- or Na- exchanged montmorillonite, hectorite, and organoclay) having a high slurry viscosity at low percent solids when mixed with fluid. Such clay minerals form a colloid where the dispersed phase and the dispersion medium produce a semisolid material, similar to jelly. Industrial applications include thickening/suspension agents, adhesives, sealants, putties and glazing compounds. Jelling viscosity is typically measured on Fann or Brookfield viscometers. For aqueous applications and some fibrous clay minerals such as palygorskite, the gelling behavior and viscosity is enhanced by adding magnesium oxide or by extruding the slurry to align the needle-shaped crystallites. For montmorillonite, gelling behavior can be enhanced by soda ash treatments to increase the exchangeable Na-cation content and the swelling capacity of the clay mineral. For solvent-based applications, various smectites can be surface modified by quaternary-amine compounds to form organoclays that display superb gelling characteristics.
See colloid

A discredited term, a mixture of pimelite and Ni-rich serpentine.

The deliberate ingestion of (specifically) soil/clay; a form of pica.
Cf., pica