CERUSSITE
Rock&Gem Magazine|February 2021
GALENA’S GIFT OF A STUNNING SECONDARY MINERAL
BOB JONES
Galena is not exactly a showcase mineral. You seldom see it prominently exhibited at shows. It does form in very attractive cubes and octahedrons and even twins, but its strong gray-black color or unusual crystal forms do not exhibit well. But what galena lacks in eye appeal, it makes up for as the source of delightful and colorful daughter minerals.

Using decomposing galena, Mother Nature produces a wonderful suite of secondary lead minerals. Reaching deep into the earth — at times over 1,000 feet in desert regions — surface waters charged with oxygen and plant acids attack deep-seated sulfide ores, including galena, breaking down to release lead ions and combine with carbonates, sulfates, arsenates, or oxides. The process produces common colorful beauties like wulfenite, mimetite, pyromorphite vanadinite, and cerussite in abundance. Rare lead minerals like leadhillite also form.

Of all the secondary lead minerals that form, the most common is not very colorful. Still, cerussite presents beautiful geometric crystals and lead carbonate known as “white lead” in the old days. Cerussite is usually transparent to translucent and is the heaviest of all the transparent crystals you’ll encounter. When colorless, it has a brilliant luster due to its lead content, which accounts for about 75 percent of its weight. Lead can give other substances a high luster. You’ve heard of brilliant Swarovski glass used in chandeliers and glass art objects, correct? It is highly lustrous leaded glass!

CERUSSITE’S STRIKING CRYSTAL FORMATION

Cerussite can also appear as color-pale tan, pale green, bluish, yellow, or some other tint due to another mineral included as an impurity. Color plays only a minor role in the mineral’s value. Far more interesting and appealing is cerussite’s almost ingrained habit of forming any one of several twin forms, all very attractive and even beautiful. Unlike most crystals that twin, made up of two crystals, cerussite goes a step beyond ordinary twinning by combining several dozen crystals to twin in a very attractive unusual physical feature. Cerussite forms a greater assortment of twin forms than any other mineral, so these twins are most appealing and valuable whether the twin is stark white, has a tint of color, or water clear.

In addition to the varied and noteworthy twinning habits of cerussite, it’s interesting to learn the mineral crystallizes in the orthorhombic system. The term “ortho” indicates that the crystal has three internal axes around which it forms. Each axis is at an aright angle, just as in a cube, like a fluorite specimen. Orthorhombic crystals have rhombic faces, which means that every orthorhombic species crystal face is slanted, not square, and angled. Still, all slanted sides are at a right angle to each other. You see this best when a cerussite crystal is tabular. But cerussite does not form simple tabular rhombs very often. Instead, it tends to develop long slender crystals with slanted faces or as twinned crystals attached at the base, at an angle of about 60 degrees.

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