PHYSICAL PROPERTIES:
Chemistry: Zn4 Si2
O7 (OH)2 -H2O
Composition: Hydrated Zinc Silicate Hydroxide
Class: Silicates
Subclass: Sorosilicates
Group: Hemimorphite
Crystal system: Orthorhombic - Rhombic
pyramidal
Fracture: conchoidal to subconchoidal
Hardness: Less than 5
Specific gravity: Apx. 3.4
Luster: vitreous
Streak: White
Cleavage: perfect in one direction
Color: greens, blue-greens, whites, colorless,
browns to yellows
Transparency: transparent to translucent
Associated Minerals: Aurichalcite,
Calcite Geothite, Limonite and Smithsonite.
COMPOSITION:
Hydrous zinc silicate (67.5% ZnO, 25.0% SiC)2,
7.5%H20)
DISTINGUISHING CHARACTERISTICS:
Its polar or hemimorphic crystals from which Hemimorphite
gets its name is the most common way to identify hemimorphite. The crystal
structure produces a different termination at each end of the crystal.
One termination is rather blunt and the opposite end is terminated like
the point of a pyramid. Other Characteristics: strongly pyroelectric
and piezoelectric. Strongly susceptible to electrical charges with changing
temperature; often fluorescent pale orange in long-wave ultraviolet
light. Distinguished from smithsonite by its lack of bubbling in acid
ENVIRONMENT:
Environment: The oxidized zone of zinc deposits.
CRYSTAL DESCRIPTION:
The bladed crystal form and the botryoidal form are
the most common. The crystals are usually elongated and flat. The terminations
are different at each end. One termination is blunted by a pedion face
that is usually beveled by several dome faces. The other end is pointed,
being capped by a pyramid. Also in rounded groups with crystallized
surfaces and in smoother botryoidal knobs, granular, massive, and earthy.
TESTS:
When heated in a test tube it gives off water and readily
becomes frosted. The coating is yellow when hot, turning white when
cold. It also fluoresces bright orange in long-wave ultraviolet, white
in short-wave ultraviolet.
LOCALITIES:
Some of the best United States specimens were
found in the Stone Mine, Leadville, Colorado, and at Elkhorn, Montana.
Excellent examples have come from Mapimi, Durango and Santa Eulalia,
Mexico. Some other nice specimens also came from New Mexico and New
Jersey
USES:
minor ore of zinc and Specimens
FACTS & HISTORY:
Hemimorphite was originally named calamine but this name has been
used for another mineral and now the name hemimorphite is in wide spread
use. Hemi means half while the morph means shape and thus the term hemimorphite
describes the interesting crystal class to which it belongs. Only a
few other minerals show hemimorphic character such as tourmaline, but
none show it as well as hemimorphite.
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