A mechanical property where a mineral breaks along a planar or near-planar structural weakness. Parting usually results from plane-like defects, often twinning, or is produced by anisotropic stress. In contrast, cleavage is a property of the periodic crystal structure.
Cf., cleavage
An obsolete term for the Fe-free variety of bixbyite, alpha-(Fe,Mn)2O3.
A poorly defined material, possibly interstratified biotite and vermiculite.
An obsolete term for trilithionite.
An obsolete term for margarite.
Having a luster similar to that of mother-of-pearl with an interplay of rainbow-like colors (iridescent).
a) Peat is partially decomposed plant (humus) matter that formed in a nominally oxygen-free, water-saturated environment, often found in northern regions where microbial activity is limited. Peat has more than 30% dry mass of dead organic matter ranging from colloidal masses to recognizable plant residues.
b) In soil science, peat soil has a high content of plant-derived organic matter (humus), usually measured by the weight loss (or loss on ignition) by dry combustion in atmosphere. In peat soils, plant residues are recognizable. If the residual weight of an oven-dried (at 105-110oC) soil after dry combustion at 440oC is less than 75% of the weight of the oven-dried soil, then the soil is considered to be peat.
The nickel analogue of chrysotile.
See pyroxenoid group.
Individual, natural soil aggregates composed of primary particles that form a soil structure. Adjoining peds are separated by planes of weakness formed by voids or cutans.