fibrous texture

mineralogy

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amphiboles

  • azurite
    In mineral: Inosilicates

    …different: amphiboles exhibit needlelike or fibrous crystals, while pyroxenes take the form of stubby prisms. In addition, the different chain structures of the two groups result in different cleavage angles.

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crystal aggregates

  • azurite
    In mineral: Crystal habit and crystal aggregation

    …flattened like a knife blade; fibrous, an aggregate of slender fibres, parallel or radiating; acicular, slender, needlelike crystals; radiating, individuals forming starlike or circular groups; globular, radiating individuals forming small spherical or hemispherical groups; dendritic, in slender divergent branches, somewhat plantlike; mammillary,

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Key People:
Marcia McNutt

lithosphere, rigid, rocky outer layer of Earth, consisting of the crust and the solid outermost layer of the upper mantle. It extends to a depth of about 60 miles (100 km). It is broken into about a dozen separate, rigid blocks, or plates (see plate tectonics).

A series of forces that include slab pull (the sinking of dense blocks into the underlying mantle), slow convection currents deep within the mantle (which are generated by radioactive heating of the interior) and ridge pushing (generated by the upwelling of mantle at divergent boundaries [such as oceanic ridges]) are believed to cause the lateral movements of the tectonic plates (and the continents that rest on top of them) at a rate of several inches per year.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by John P. Rafferty.