smithsonite588

SMITHSONITE:

PHYSICAL CHARACTERISTICS:

Color is commonly apple green, blue-green, lavender, purple, yellow and white as well as tan, brown, blue, orange, peach, colorless gray, pink and red.

Luster is usually pearly to resinous with light play across its surface and sometimes is simply vitreous.

Transparency: Crystals are transparent to translucent.

Crystal System is trigonal; bar 3 2/m

Crystal Habits include the rhombohedrons and scalenohedrons with generally curved faces. But more commonly is botryoidal or globular.

Cleavage is perfect in three directions forming rhombohedrons.

Fracture is uneven.

Hardness is 4 - 4.5.

Specific Gravity is approximately 4.4 (heavy for nonmetallic minerals)

Streak is white.

Associated Minerals are those found in oxidation zones of zinc sulfide deposits such as hemimorphite, cerussite, wulfenite, limonite, mimetite, dolomite, hydrozincite, aurichalcite, calcite and other carbonate minerals.

Other Characteristics: Effervesces slightly with warm hydrochloric (HCl) acid.

Noteable Occurrences include Tsumeb, Namibia and the Broken Hill Mine in Zambia; the Kelly Mine, Magdalena, New Mexico; Leadville, Colorado; Utah; Idaho and Arizona, USA; Mexico; Laurion, Greece; Bytom, Poland; Moresnet, Belgium and many other localities.

Best Field Indicators are luster, typical botryoidal habit, cleavage, hardness, reaction to hot acids and density.

Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.

Gypsum has several variety names that are widely used in the mineral trade.

"Selenite" is the colorless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the greek for Moon and means moon rock.

Another variety is a compact fiberous aggregate called "satin spar" . This variety has a very satin like look that gives a play of light up and down the fiberous crystals.

A fine grained massive material is called "alabaster" and is an ornamental stone used in fine carvings for centuries, even eons.

Crystals of gypsum can be extremely colorless and transparent, making a strong contrast to the most common usage in drywall. The crystals can also be quite large. Gypsum is a natural insulator, feeling warm to the touch when compared to a more ordinary rock or quartz crystal. Sheets of clear crystals can be easily peeled from a a larger specimen.

Smithsonite is named for James Smithson, the founder of the Smithsonian Institution. The luster of smithsonite sets it apart from other minerals: it has a silky to pearly luster giving natural specimens a certain play of light across its surface that resembles the fine luster of melted wax glowing under a candle flame. It is easy to wax poetically when discussing smithsonite's unique luster. It is really unusual and captivating and collectors can easily get hooked.

Smithsonite in addition to wonderful luster also has a varied color assortment. The apple green to blue-green color is probably smithsonite's most well known color, but it is its purple to lavender color that is probably its most sought after hue. There also exists attractive yellow, white, tan, brown, blue, orange, peach, colorless, pink and red smithsonite specimens and all of them are a credit to this mineral.

The typical crystal habit of smithsonite is an interesting form called botryoidal. This form has the appearance of grape bunches and is the result of radiating fibrous crystals that form from central attachment points and grow outward and into each other. The result is a rounded, bubbly landscape for which smithsonite is considered the classic example. There are also other habits more typical of Calcite Group minerals including rounded rhombohedrons and scalenohedrons. Most of these come from the famous mines of Tsumeb, Namibia and the Broken Hill Mine in Zambia. The Tsumeb specimens are colored by trace amounts of cobalt and can have some real exotic colors. The Kelly Mine, Magdalena, New Mexico has produced the absolute finest blue-green botryoidal masses of smithsonite. But there are many localities that have or are producing excellent specimens.

"The Mineral Smithsonite"

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