HEMIMORPHITE

This article appears in Volume V13, Page 258 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: HEG-HIG

HEMIMORPHITE , a

mineral

MINERAL

consisting of hydrous zinc silicate, H2Zn2SiO5, of importance as an ore of the metal, of which it contains 54.4%. It is interesting crystallographically by reason of the

hemimorphic

HEMIMORPHIC

development of its orthorhombic crystals; these are prismatic in habit and are differently terminated at the two ends. In the figure, the faces at the upper end of the crystal are the basal plane k and the domes o, p, 1, m, whilst at the lower end there are only the four faces of the pyramid P. Connected with this polarity of the crystals is their pyroelectric characterwhen a crystal is subjected to changes of temperature it becomes positively electrified at one end and negatively at the opposite end. There are perfect cleavages parallel to the prism faces (d in the figure). Crystals are usually colourless, some-times yellowish or greenish, and transparent; they have vitreous lustre. The hardness is 5, and the specific gravity 3.45. The

mineral

MINERAL

also occurs as stalactitic or botryoidal masses with a fibrous structure, or in a massive, cellular or granular

condition

CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

intermixed with calamine and clay. It is decomposed by hydrochloric acid with gelatinization; this property affords a ready means of distinguishing hemimorphite from calamine (zinc carbonate), these two minerals being, when not crystallized, very like each other in

appearance

APPEARANCE (from Lat. apparere, to appear)

. The water contained in hemimorphite is expelled only at a red heat, and the mineral must therefore be considered as a basic metasilicate, (ZnOH)2SiOa.
The name hemimorphite was given by G. A. Kenngott in 1853 because of the typical

hemimorphic

HEMIMORPHIC

development of the crystals. The mineral had

long

LONG, GEORGE (1800-1879)
LONG, JOHN DAVIS (1838– )

been confused with calamine (q.v.) and even now this name is often applied to it. On account of its pyroelectric properties, it was called electric calamine by J. Smithson in 1803.
Hemimorphite occurs with other ores of zinc (calamine and

blende

BLENDE, or SPHALERITE

), forming veins and beds in sedimentry limestones. British localities are Matlock, Alston, Mendip Hills and Lead-hills; at Roughten Gill, Caldbeck Fells,

Cumberland

, it occurs as mammillated incrustations of a sky-blue colour. Well-crystallized specimens have been found in the zinc mines at Altenberg near Aachen in Rhenish Prussia,

Nerchinsk

NERCHINSK
NERCHINSK (in full NERCHINSKIY ZAVOD)

mining

district

DISTRICT

Siberia

SIBERIA

, and Elkhorn in Montana. (L. J. S.)

End of Article: HEMIMORPHITE

If you wish, you can link directly to this article.

<a href="http://jcsm.org/StudyCenter/Encyclopedia/HEG_HIG/HEMIMORPHITE.html">
HEMIMORPHITE
</a>

(Previous)
HEMIMORPHIC

(Next)
HEMINGBURGH, WALTER OF

JCSM was founded in 1997 and exists to help the community and bring people into a life-changing and productive relationship with Jesus Christ. JCSM offers over 200,000 free web pages, including its weekly inspirational emails that were sent continuously for over a decade.

Jesus Christ Saves Ministries
P.O. Box 9297
San Diego, CA 92169
1-888-887-0417 or Email