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The Mineral hemimorphite

Hemimorphite Crystal Fan

Hemimorphite is a unique mineral, with different crystal terminations on each side of a single crystal. This habit is responsible for Hemimorphite's name, from the Greek hemi, meaning "half" and morph, meaning shape. Although this habit is very common among Hemimorphite crystals, its visibility is usually obscured by one end of a crystal being attached to the matrix.

Prior to 1803, Hemimorphite and Smithsonite were thought to be the same mineral, called Calamine. In 1803, James Smithson, a British mineralogist, discovered that these were two distinct zinc mineral species that closely resembled each other. 

Hemimorphite is a mineral of two main distinct patterns: A well-crystallized form, and a microcrystalline globular form. These two types of Hemimorphite appear entirely different from each other, and it surprising that they are of the same mineral.

Chemical Formula

Zn4Si2O7(OH)2 · H2O

Color

White, colorless, beige, yellow, light brown, blue. Rarely greenish or yellow.

Crystal System

Orthorhombic

Properties

Streak
Colorless
Hardness
4.5 - 5
Transparency
Transparent to translucent
Specific Gravity
3.4 - 3.5
Luster
Crystals are Vitreous to adamantine. Globular forms are vitreous, waxy, silky, or dull.
Cleavage
1,1
Fracture
Subconchoidal to uneven
Tenacity
Brittle
Other ID Marks
1) Strongly pyroelectric.
2) May fluoresce pale orange in longwave ultraviolet light.

Crystal Habits

Crystals are flattened prismatic and tabular, and are usually in platy groupings. Also bladed, in fan shaped groupings, radiating, acicular, coxcomb, in rosettes, and drusy. Crystals grow in distinctive hemimorphic habits. Most commonly in globular form such as botryoidal, mammilary, and stalactitic groupings. 

3D Crystal Atlas

Additional Information

Composition
Basic hydrous zinc silicate
In Group
Silicates; Sorosilicates
Striking Features
Crystal forms and habits, and mode of occurrence
Environment
In the oxidation zone of hydrothermal replacement deposi
Rock Type
Sedimentary, Metamorphic

Other Names

Calamine Calamine was the original name of the mineral Hemimorphite, and described this zinc ore in globular and botryoidal forms. The mineral Smithsonite, which closely resembles Hemimorphite and is also a zinc ore, was also called Calamine by the miners and early collectors. Today use of this term has been discouraged because of its confusion of mineral species.

Uses

Hemimorphite is an ore of zinc in zinc deposits. It is also an important mineral for collectors, especially when well-crystallized and in globular blue forms. Hemimorphite is also used as a collectors gemstone, with the blue forms polished into cabochons for collectors of rare gemstones.

Noteworthy Localities

Hemimorphite is found in many localities worldwide, though most only produce microcrystals of this mineral. However, there are many exceptional localities though that have provided excellent mineral specimens. In Europe, some of the earliest occurrences of Hemimorphite were at Vieille Montagne, Kelmis, Belgium. Blue globular and white crystallized forms of this mineral are found in Germs-sur-l'Oussouet, Lourdes, France; and at the Sa Duchessa Mine, Domusnovas, Sardinia, Italy. Colorless and white Hemimorphite crystals, sometimes associated with Wulfenite, have come from Bleiberg, Carinthia, Austria; and white crystal fans from Lavrion District, Attiki, Greece.

China has recently been producing some outstanding globular forms Hemimorphite with a deep, neon blue color. The most notable localities are Dulong and Wenshan, Yunnan Province. In Iran, nice white crystals are found in the Qaleh-Zari Mine, Nehbandan.

In Africa, pale blue, spiky Hemimorphite crystals come from the Skorpion Mine, Rosh Pinah, Namibia; and light blue rounded aggregates are found in M'Fouati and Mindouli, Congo.

Mexico is probably the most prolific country when it comes to collectible specimen production of Hemimorphite. The famous Ojuela Mine in Mapimi, Durango is one of the most prolific Hemimorphite localites, forming well-shaped crystals on a Limonite matrix. Very large white crystals and fans have been found at Santa Eulalia, Chihuahua; and toothpaste-blue botryoidal Hemimorphite has come from the Santo Niño Mine, Santa María del Oro, Durango.

In the U.S., globular masses of Hemimorphite are well-known from the Sterling Hill Mine, Ogdensburg, Sussex Co., New Jersey. This locality has produced rounded white aggregates and sparkling drusy crystals. Tan and yellow Hemimorphite has come from Granby, Newton Co., Missouri; and Joplin, Jasper Co., Missouri, often as epimorphs and coatings.

Very large, white and colorless Hemimorphite  crystals come from the Summit Mine, Radersburg District, Broadwater Co., Montana; and dense white crystal aggregates from Leadville District, Lake Co., Colorado. The 79 Mine near Hayden, Gila Co., Arizona, has produced Hemimorphite in beautiful, lightly-colored blue and greenish rounded aggregates.

Common Mineral Associations

Calcite, Hematite, Limonite, Smithsonite, Galena, Aurichalcite, Rosasite, Mimetite

Distingushing Similar Minerals

Smithsonite - Heavier and effervesces in acid.
Cerussite and Barite - Much heavier.


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