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| Google Earth © view of Canada del Oro and Sutherland Wash near Catalina State Park. |
The annual Tucson Shows have begun. The Day 1 for many shows was on Saturday
January 31, a day of rather rare desert precipitation in the city. In fact, the Mt. Lemon area in the Santa Catalina
Mountains (that dominate the Tucson skyline) received in excess of five inches
of rain. Several of the area rivers,
normally rather dry in most years, were roaring and quite impressive. Canada del Oro in Oro Valley near Catalina
State Park, my temporary home, was booming and carrying a wide selection of
sand, pebbles and cobbles. Sutherland
Wash, a tributary of Canada del Oro in the Park, actually pushed enough “sand”
onto the only access road and closed the campground to visitors getting “in or
out.” It was great to observe such a
massive desert winter storm and see associated erosional and depositional processes.
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Sutherland Wash drains the bajadas coming off the
western flank of the Catalina Mountains.
During times of high rain fall the Wash funnels (right to left) large amounts of “sand”
toward the master stream, Canada del Oro (hidden to the left), and often deposits the sediment in
and on the major road leading to the Park campgrounds.
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I spent my first show day, on Monday, visiting the
Arizona Mineral and Fossil Marketplace on north Oracle Street. Essentially, the show is the first cluster of
tents as one drives south on Oracle toward the city center. There are some small time “mom and pop”
dealers in the tents and I am especially partial to a couple of them. Both have a wide selection of moderately-priced
(sometimes cheap) minerals as well as
some beautiful three figure specimens.
However, I am most interested in purchasing specimens to supplement my
collection that are on the lower end of the price selection. And, these small dealers are more than
willing to indulge in conversation with “ordinary” citizens and rockhounds.
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Rock Deco is a locally owned (Tucson) shop
specializing in Arizona minerals at a reasonable price.
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So, what was my best purchased specimens costing
five bucks or less? Today it is a hand
specimen of vanadinite crystals scattered on a bed of calcite collected from the
San Carlos Mine (Apex Mine) in San Carlos, Mun. de Manual Benavides, Chihuahua,
Mexico. I could not locate much geological
information on the San Carlos area except Moore (2008) noted “the San Carlos
replacement deposit of argentiferous galena, mined briefly in the late 19th century
and again from ca. 1930 to 1952, has produced beautiful and distinctive
vanadinite specimens, as well as a limited number of superb wulfenite
specimens.”
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Gemmy calcite matrix with scattered tan vanadinite
crystals (largest is ~5 mm). Width of bottom specimen ~12 cm. Upper photo is a closer view.
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The calcite matrix is rather gemmy and fluoresces a nice green color with my
UV light. The vanadinite crystals,
intergrown in the calcite rhombs, are elongated and euhedral, up to 5 mm in
length, are tan to tan-orange in color, and have the typical barrel shape in
cross section. One dealer told me that
most specimens like this were mined during the 1970s and 1980s and very few
have come out in the last 25 years.
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Photomicrograph of a ~4.5
mm vanadinite crystal. The cross sectional view shows the typical hexagonal
shape.
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Vanadinite is a lead chlorvanadate [Pb5(VO4)3Cl]
with hexagonal crystals, various hues of red to orange to brown in color, less
than adamantine in luster, and soft at ~2.5-3.0 in hardness (Mohs). It
forms a solid solution with pyromorphite (lead chlorophosphate) and mimitite
(lead chloroaresnate). MinDat notes it is a secondary mineral found in the “oxidation
zone of lead deposits in arid climates resulting from the alteration of
vanadiferous sulphides and silicates of the gangue and wall rocks.” My question is: what sulfide (primary zone)
in the Apex mine contains vanadinite?
The list of 17 minerals noted in MinDat does not list a sulfide that is
obviously, at least to me, a “vanadiferous sulphide.” Of course I am far from any sort of a petrologist.
I found it interesting that Professor del Rio
(School of Mines of Mexico) discovered the mineral vanadinite (brown lead) in
1801before Niles Sefstrom “discovered” the element vanadium in 1830. Del Rio knew that his “brown lead” contained
a new element which he named erythronium but later recanted his name.
So, the big event is off and running and I am
excited for the chance to explore.
REFERENCES
CITED
Moore, Thomas, 2008, Famous Mineral Localities: The
Apex Mine, San Carlos, Chihuahua, Mexico. Mineralogical Record v. 39 no. 6.