See pyrosmalite.

An orthorhombic (space group Pbca) pyroxene, with an end-member composition of Fe₂Si₂O₆. End-member ferrosilite does not occur under normal pressure conditions, with the assemblage of fayalite and quartz thermodynamically more stable than ferrosilite. Ferrosilite is thus rare, but it has been found in mafic rocks and some high-grade metamorphosed banded iron formations.
See pyroxene group for additional details.

See pyroxenoid group.

See stilpnomelane.

See pneumoconiosis.

A crystal habit describing thin, flexible filaments.

In geotechnical engineering, fill is geological material in containment formed by human activities, such as dumping, compaction, and hydraulic deposition (via pumping).

A filler is a solid fine- to very fine-grained, natural or synthetic, organic or inorganic substance that bonds to the active ingredients, e.g. clay minerals, with the following properties:

1. negligible dissolution in the active material and

2. capable of being added to the excipient to reduce the amount of the active ingredients (= cost savings) without a significant reduction in the properties of the active material or to improve its properties. For example, talc and kaolinite are used as fillers in paper, cosmetics, pigments, or varnishes, and smectite is often used as a filler in plastics.

A kaolinitic-rich clay with excellent refractory properties, and the fired product is commonly used as fire bricks. The refractory clays are classed as low, medium, high, and super duty with the latter heat resistant from 1430 to 1804°C. Fire clays are low in alkali, alkali earth, and transition metals. Typically found in association with coal layers.
See refractory material.
Cf., underclay, seat rock

Heat treatment of clay materials that cause partial melting and fusion to create ceramics
Cf., thermal activation