Smithsonite

Smithsonite occurs in a wide variation of colors. Its typical globular habit and often vibrant colors make this a desirable mineral for collectors. Smithsonite is composed of zinc carbonate, but the zinc may be partially replaced with other elements. Those elements are responsible for the color variations. For example, copper  often causes green or bright blue colors, and cobalt causes a pink to purple color. Cadmium makes Smithsonite yellow, and iron gives it a brown to reddish-brown color.

Smithsonite rarely occurs in visible crystals. The only two locations to produce large crystals of significance are Tsumeb, Namibia; and the Kabwe Mine (Broken Hill), Zambia. Virtually all other findings of this mineral are in globular or botryoidal-like forms. Many of the rounded forms have a very distinct feathery or sparkling light effect. Botryoidal Smithsonite aggregates are sometimes lubricated with oils by dealers to enhance luster and appeal to collectors.

Smithsonite belongs to the calcite group of minerals, a group of related carbonates that are isomorphous with one another. They are similar in many physical properties, and may partially or fully replace one another, forming a solid solution series. All members of the calcite group crystallize in the trigonal system, have perfect rhombohedral cleavage, and exhibit strong double refraction in transparent rhombohedrons.

Smithsonite is named in honor of James Smithson, the founder of the Smithsonian Institution.

Mainly globular, botryoidal, stalactitic, and concretionary. Occasionally occurs as lenticular lumps, encrusting, massive, grainy, and as banded formations. Masses are sometimes porous. Crystals are rhombohedral and scalenohedral, and usually are rounded with curved faces. Crystals may contain triangular growth patterns.

Smithsonite is also known to form pseudomorphs of other minerals such as Calcite, Galena, and Fluorite, assuming the crystal shapes of those minerals.

Large Smithsonite crusts are found in a number of areas on the island of Sardinia, Italy, particularly at the Massua and Monteponi Mines, in Iglesias. Blue-green botryoidal masses and crusts are common at the mines at Lavrion, Greece.

Individual Smithsonite crystals and crystal clusters of all colors are well-known from Tsumeb, Namibia. Two other African localities which provided visible crystals of this mineral are Berg Aukas, Grootfontein, Namibia; and the Kabwe Mine (Broken Hill), Zambia. The famous Australian locality of Broken Hill, New South Wales, is known for its abundance of minerals including Smithsonite.

Mexico has two outstanding Smithsonite localities which contain beautifully colored Smithsonite, including deep pink and electric green colors. These are the Refugio Mine, Choix, Sinaloa; and the San Antonio Mine, Santa Eulalia District, Chihuahua.

The U.S. has many fine Smithsonite occurrences; perhaps the most famous being the Kelly Mine, Magdalena, Socorro Co., New Mexico. The No. 79 Mine, Hayden, Gila Co., Arizona is known for its dark and apple-green Smithsonite. Bright yellow and orange-yellow specimens have come from Rush, near Yellville, Marion Co., Arkansas. A large industrial zinc deposit produced Smithsonite in Leadville, Lake Co., Colorado. Other localities are Cerro Gordo, Inyo Co., California; the Hidden Treasure Mine, Ophir Hill, Tooele Co., Utah; and Mineral Point, Iowa Co., Wisconsin.