TUCSON: BEYERITE, TALMESSITE, & HIDALGOITE

As I noted in my last posting I will not make it to all 51 of the Show venues—not enough days in the two weeks and not enough hours left in my legs.  So, I pick the venues carefully (I am not interested in the thousands of Moroccan fossils, along with vanadinite, that fill many venues).  I am now off to the Mineral Habit venue, a Show that is “”new to Tucson.  Actually, the dealers moved out of the “Slaughterhouse” on Grant Avenue to vacated buildings on north Oracle—a good move with nicer facilities.  The group of dealers is anchored by Shannon Family Minerals, an internet dealer. with a huge inventory.  Mike Shannon always has some interesting, and often rare, minerals for sale. 

I picked up a thumbnail of beyerit (beyerite in the U.S.) with an old German label: Johann Friedrich Mine, Murgtal, Schwarzwald.  The Murg is a tributary of the Rhine River while Schwarzwald is German for what we call the Black Forest.  Both are in the State of Baden-Württemberg in the southwest part of Germany bordering France. The only reference I could find for the Johann Friedrich Mine was in MinDat and labeled as: Königswart Mine (Johann-Friedrich Mine), Schönegründ, Baiersbronn, Freudenstadt, Karlsruhe, Baden-Württemberg, Germany.  So, I will go with Mindat: Copper-Silver-Bismuth mineralized veins in sandstone. The mine was abandoned in 1826.

Beyerite is a bismuth oxycarbonate [has both oxide and carbonate anions], Ca(BiO)₂(CO₃)₂, and forms as a secondary mineral in oxidation zones of bismuth-bearing sulfates or sulfides, or perhaps native bismuth. However, I am uncertain about the Johann Friedrich as MinDat did not list any of these hypogene minerals, such  as bismuthinite, as being present although nearby mines have this primary ore mineral.
 

Crusts of gray to green beyerite.  Width FOV 9 mm.

Lathes of tan to light green beyerite each about 1 mm in length.

Beyerite has a variety of colors ranging from yellow to white to gray and shades in-between.  It is quite soft (2.0-3.0; Mohs), transparent to translucent, and has a luster ranging from dull to adamantine.  It belongs to the Orthorhombic Crystal System, but crystals are often hard to distinguish in earthy masses.  Some beyerite appears as flattened rectangular plates, or spheres of radiating fibers, or simply individual lathe-like crystals.

Beyerite is pretty “plain looking” in most cases and MinDat notes “it is visually indistinguishable from other oxycarbonates bismutite [(BiO)₂CO₃] and kettnerite [CaBiCO₃OF].”  So, my specimen is listed as beyerite; however, the label is “old” so perhaps quantitative work has not been performed of these specimens from the Johann Friedrich mine.  MinDat lists both beyerite and bismutite as coming from the mine.

I am always on the hunt for mineral specimens from Utah.  I have written other posts about the Gold Hill mine located in the western part of the state as it has produced a fantastic suite of minerals. Gold Hill is an old mining community located south of the bi-state town of Wendover, Nevada/Utah, that was mined for gold, copper, zinc, lead, arsenic and tungsten from the mid to late 1800s until the late 1940s.  The peak activity was in the early 1900s when a spur railroad reached the area in 1917.  There was only sporadic mining after World War I.

Gold Hill, or the Clifton District, contains numerous mines, including an open pit, and is located near the northwest end of the Deep Creek Mountains, perhaps Utah’s most isolated and unknown mountain range.   Peaks do reach 12,000 feet—Ibapah Peak at 12,087 and Haystack at 12,020.  The Deeps are the major topographic feature in western Utah.  The range has a Precambrian core surrounded by Paleozoic sedimentary rocks with later Mesozoic intrusions—mostly quartz monzonite and granite/granodiorite, and later Tertiary volcanics.  

Prismatic/stalactitic and translucent crystals of calcite, each 1-3 mm in length.  I am uncertain about spray of much smaller translucent crystals in the center.  Top photomicrograph has small,1 mm "balls" of austinite crystals (A) between the larger calcite crystals. 

A "ring" of talmessite crystals surrounded by very tiny austenite crystals and surrounding massive goethite.  Width FOV ~9mm. 

Gold Hill is home to an amazing number of arsenate minerals, those with the AsO₄ 3- oxidation state anion (arsenic has a 5+ oxidation state while the oxygen has an oxidation state of 2- for a total state of 3-).   One of the rare arsenates present is talmessite, a hydrated calcium magnesium arsenate: Ca₂Mg(AsO₄)₂-2H₂O).  The mineral has a vitreous luster and is  colorless or white; however, small amounts of nickel may turn it a pale green while cobalt will impart a characteristic pink shade.  Is has a hardness of 5.0 (Mohs) and is transparent (colorless) to translucent (white). Crystals may form massive crusts, prismatic/stalactitic groups, or aggregates of radiating fibrous microcrystals.  MinDat notes that talmessite is an oxidation product of realgar/orpiment (arsenic sulfide) or copper-nickel arsenides (such as skutterudite) and forms in the oxidation zones of hydrothermal ore deposits. 

Crust of green hidalgoite.  Width FOV 1.3 cm.

 

Boxwork of green hidalgoite.  Width FOV on above two microphotographs ~1.0  cm.

Another interesting Gold Hill arsenate picked up at the Mineral Habit venue is a rally nice specimen of hidalgoite:  PbAl₃(AsO₄)(SO₄)(OH)_6.  Hidalgoite is sort of non-descript usually occurring as a druse or spherulitic encrustation; however, at the type locality (Zimapan Mining District, Hidalgo, Mexico) the mineral occurs as dense white masses.  In some localities the mineral is colorless; however, the specimens I have observed from Gold Hill are tan to orange to shades of green.  In addition, the Gold Hill specimens are usually associated with “limonite” and secondary rust coloration may hide the true color.  and is a product of weathering in the oxide zone of metallic sulfide deposits (containing lead).  Hidalgoite is sort of non-descript usually occurring as a druse or spherulitic encrustation; however, at the type locality (Zimapan Mining District, Hidalgo, Mexico) the mineral occurs as dense white masses.  In some localities the mineral is colorless; however, the specimens I have observed from Gold Hill are tan to orange to shades of green.  In addition, the Gold Hill specimens are usually associated with “limonite” and secondary rust coloration may hide the true color.  The luster is rather dull/earthy, the streak is white, and the hardness is around 4.5. It is often porous with numerous voids and is brittle with a conchoidal fracture.  Hidalgoite is found in the oxide/secondary zone of polymetallic lead sulfide deposits.

So, it was a good day for collecting interesting minerals in the shops.