New Mexico Mineral Symposium — Abstracts

Vanadinite, the mineral
Vanadinite is a lead chloro vanadate Pb₅(VO₄)₃Cl. A partial series exists toward the arsenate mimetite, and the phosphate pyromorphite. Arsenic-rich vanadinite is generally known as endlichite.

Vanadinite crystallizes in the hexagonal system, usually as simple short to long prisms terminated by the pinacoid. Crystals are often cavernous, and sometimes barrel-shaped. It has a hardness of 3, and a density of 6.88. The color is usually red, also brown, orange, yellow, and rarely green. The streak is white to yellowish, and the luster is subresinous.

Occurrence—Vanadinite is a secondary mineral found in the oxide zone of lead and vanadium bearing deposits. Associated minerals include pyromorphite, wulfenite, cerussite, anglesite, descloizite and mottramite. Vanadinite alters to descloizite and sometimes replaces wulfenite.

Uses—Vanadinite is a minor ore of the metal vanadium that is alloyed with steel to toughen it.

Vanadinite in Arizona
Arizona has the most vanadinite localities of any state in the Union (Anthony et al., 1995, list 63). The majority are in the southern Basin and Range province. In most of these deposits it is a minor secondary mineral thought to be derived from large associated bodies of granitic and monzonitic rocks. Most mining of vanadium has occurred in the north part of the state on the Colorado Plateau. These deposits are the so called Plateau-type deposits, occurring in sandstones. Uranium is the other major and far more economically important component of these deposits. Unfortunately, the minerals of these deposits rarely crystallize and therefore are of little interest to mineral collectors.

Several Arizona localities are world-famous for both the quality and quantity of their vanadinite as well as the associated minerals. The best known are the Apache, Old Yuma, and the Mammoth-St. Anthony mines. Recent additions to Arizona's list of classics include the J. C. Holmes claim, Puzzler mine, North Geronimo (Pure Potential) mine, and the Hamburg mine.

References:

1. Anthony, J. W., Williams, S. A., Bideaux, R. A., Grant, R. W., 1995, Mineralogy of Arizona: University of Arizona Press, Tucson, 3rd edition.