Penninite

penninite

[′pen·ə‚nīt]

(mineralogy)

(Mg,Fe,Al)₆(Si,Al)₄O₁₁(OH)₈ An emerald-green, olive-green, pale-green, or bluish mineral of the chlorite group crystallizing in the monoclinic system, with a hardness of 2-2.5 on Mohs scale, and specific gravity of 2.6-2.85.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Penninite

 

(also pennine; named after the Pennine Alps, where the mineral was first discovered), a mineral of the chlorite group, widely distributed in metamorphic rocks, with the approximate chemical formula (Mg, Fe)₅•Al[AlSi₃O₁₀](OH)₈. Penninite crystallizes in the monoclinic system to form minute, flat, micaceous crystals with perfect cleavage. It generally occurs as solid, scaly masses or as soft, flexible individual scales. Its color varies from green to blackish green, except for the chromium-rich penninites, such as rhodochrome and kammererite, which are pink, violet, or carmine. Penninite has a hardness of 2.0–2.5 on Mohs’ scale and a density of 2,600–2,850 kg/m³. It is formed as a secondary mineral during the metamorphism of ferromagnesian silicates, such as olivine, enstatite, hornblende, and biotite.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.