MINERALS FROM THE BRIDING ESTATE SALE: PART I

 

The Colorado Springs Mineralogical Society lost a long-time member, Laurann Briding, in June 2020. Laurann was an active rockhound and had a large collection of both purchased and personally dug specimen.  Recently the family had the rock/mineral estate appraised by local dealer Leonard Himes and material was then turned over to Rebecca Nohe Estate Sales for disbursement on August 7-9.  Most of the material was sold by flats ranging in price from $5 to $1000 and hundreds of micromounts were available for a buck per piece.  There were also several individual cabinet specimens highlighted by a $5000 rhodochrosite from the famous Sweet Home Mine near Alma, Colorado.  Perhaps the most interesting item in the sale was a brass microscope owned by the CSMS founder and Honorary President for Life, Lazard Cahn.  That was a real find and I was hoping that a benefactor would purchase the scope and turn it over to a museum.

A brass microscope once owned by Lazard Cahn, the Honorary President for Life of the Colorado Springs Mineralogical Society.

 

 Lazard Cahn, ~1930.  Photo © courtesy of the Digital Collections at the Pikes Peak Library District.

The Sweet Home Mine rhodocrosite sold on Saturday morning for the asking price, $5000.  Notice the reflecting mirror in the back of the showcase.

A large selection of micromounts were available and a few are shown above. I was able to pick up a couple of micro flats on a return visit Sunday noon.

 Specimens and jewelry were tastefully displayed by Rebecca.

Due to Covid-19, I was hesitant to head out into a public area since I have pretty much self-quarantined at home since late March.  But, access to the show room was limited and by appointment only (30 minutes only) and masks were required. So off I went to check out the goodies.  As noted in my last posting, my best purchase was a nice specimen of the hydrated zinc arsenate legrandite [Zn₂(AsO₄)(OH)-(H₂O)], a very collectable mineral due to its color and rarity. But I did purchase a few other minerals with good specimens scattered in the flats.

When rockhounds think of collectable amethyst the concretions from Brazil pop into their mind.  Ask them about amethyst from Mexico and the gemmy quartz crystals from Vera Cruz are probably in their collection.  However, amethyst from the Guanajuato silver mines are probably not familiar to most rockhounds.  And speaking of silver, the Guanajuato mining district is one of the most prolific and best-known silver districts in the world. Silver was discovered in 1548 and estimates of historic production range from 700 million to 1.5 billion oz of silver, as well as 4.0 million to 7.0 million oz of gold. Guanajuato was a major center of a Spanish colonial mining boom; in-fact at one point, the La Valenciana mine to the north of the city accounted for up to two third of the worlds silver production. Within 20 miles of Guanajuato’s downtown there are at least eight major metal mines either in production, in development or recently closed, as well as a flurry of exploration activity.  To the non rockhounds, Guanajuato may be best known as the home of painter Diego Rivera, the husband of painter and political activist Frida Kahlo.

The Guanajuato mines are classified as “epithermal vein deposits” where a variety of minerals are located in veins that are probably the result of previous fractures and cracks in the host rock.  The hydrothermal brines, especially sodium-calcium-chloride brines, are effective solvents and are able to dissolve the primary sulfide ores and circulate through the host rocks.  As these brines begin to cool, usually at shallow depths, deposition of minerals take place and often these veins of minerals are quite rich.  In fact, epithermal gold deposits are some of the richest gold deposits in the world. At Guanajuato mineralization consists dominantly of silver sulfides and sulfosalts (a metal + semi-metal + sulfur), base metal sulfides (metal + sulfur) mostly chalcopyrite, galena, sphalerite, and pyrite, and electrum (alloy of silver and gold). Gangue minerals (the waste rock) are generally quartz and calcite; the host rocks (holding the minerals) are Mesozoic sedimentary and intrusive igneous rocks and Tertiary volcanic rocks (Morgan and others, 2014).

 Amethyst base with showy, snow white, rosettes of micro calcite crystals. Width FOV ~4.7 cm.

 I did not come home with a piece of silver or gold but did acquire a showy purple and white specimen with a base of gemmy terminated crystals of amethyst covered with rosettes of tiny snow-white crystals of calcite.  I could not locate information on the collector although the label appears to have some age and originally sold for $6.

Another specimen in the acquired mixed flat is a really nifty piece that has a core and base of white, well formed, dolomite crystals with a partial crust of surficial brownish-black to reddish-brown, botryoidal (individual botryoids ~4 mm) goethite.  In cross-sectional view the botryoids are composed of radiating (from the center) long prismatic crystals that have a metallic luster and a steel-gray color.  There are also tuffs or sprays of steel-gray or orange acicular goethite “sticking up” between some of the botryoids.   A second round of goethite consists of tiny (less than 1 mm) black “balls” scattered randomly across exposed dolomite crystals.  There are also: 1) numerous well-formed pyrite crystals mixed in with the micro balls; 2) a single large calcite crystal; 3) a few splotches of chalcopyrite; and 4) a hunk of massive, red hematite. All-in-all, it is an attractive specimen.

A base of white dolomite crystals with scattered micro balls of black goethite, larger black botryoidal goethite along top of specimen, scattered "clumps of pyrite, especially right, and a single large calcite crystal. Length of specimen ~ 9 cm.

Reverse of above specimen.  Note the bright red, massive hematite and the black botryoidal goethite.

Scattering of micro balls of goethite on dolomite crystals with scattered small pyrite crystals.  Width FOV ~1.7 cm.

A grouping of botryoidal goethite with hematite above and calcite and pyrite crystals.  Width FOV ~1.7 cm.

Massive hematite with micro cubes of pyrite.  Note sprays of goethite in lower right. Width FOV ~1.7 cm.

Cross sectional view of the large goethite botryoids showing acicular crystals. Width FOV ~1cm.

Sprays of gold/orange/black sprays of goethite with some nice pyrite crystals.  Width FOV ~7 mm.

The specimen came from Wawa, Ontario, Canada, a town/township/area located near Lake Superior north of Sault Ste Maria and situated in a rugged sparsely populated area. Gold and iron mines and prospects dot the area and today there seems to be a mini gold rush in progress.  The kimberlites in the area have produced diamonds and they also attract prospectors.  As best I can determine the bedrock is Archean (old Precambrian.

The specimen has an old typed label from Wallings Collector, Westbury, L.I., NY. The address seems to indicate pre-Zip Code days, so it evidently was collected before 1963.

In order to keep the file size reasonable, I have split information about minerals of the estate sale into several manageable sections. There is more coming and the previous post highlighted the zinc arsenate legrandite.

 

THE HOLY GRAIL: LEGRANDITE FROM MEXICO

 

The latest issue of Rocks and Minerals (July/August 2020, Vol. 95, No. 4) had a great article entitled Legrandite: Ojuela Mine, Mapimi, Durango, Mexico written by Malcolm Southwood and Peter Megaw.  It tells a fascinating story about finally discovering the Type Locality (Flor de Peña Mine, Nuevo Leon, Mexico) of legrandite, the mining engineer who furnished the name (Louis Charles Antoine Legrand; 1861-1920), and stories about beautiful specimens from the more famous Ojuela Mine.  Flor de Peña Mine is a small mine without much history that essentially is only known as the Type Locality for legrandite.  My specimen was picked up at Ackley’s Rock Shop before it closed several years ago; however, at one time it belonged to Willard Wulff (1904-1998) a well-known micromounter in Colorado Springs, a Charter Member of the Colorado Springs Mineralogical Society, and a “student” of Lazard Cahn.  The Wulff name is on the micromount box and a label said, “Flor de Peña Mine, Lampazos de Naranjo, Nuevo Leon/Mexico/TYP”.” Since it was for sale in a rock shop, I suspect someone may have acquired it from Wulff and it then went to Ackley’s. I do not have the slightest idea how Wulff acquired the specimen (most likely not self-collected) except probably by trading or buying.  Another possibility might be a purchase or trade from one Louis Pardo who operated Pardo’s Rocks and Minerals in Tucson, Arizona from 1948-1972. The slight clue is I acquired a second legrandite micromount at the Wulff estate sale (a few years ago) stating it was collected from Santa Eulalia, Mexico, with the names Wulff and Pardo affixed as the label.  I presume this means that Wulff acquired the specimen from Pardo.

Legrandite is a hydrated zinc arsenate [Zn₂(AsO₄)(OH)-(H₂O)] and a very collectable specimen due to its color and rarity.  The prismatic crystals are usually a beautiful bright- to wax- yellow color (perhaps ranging to dull orange and rarely colorless) with a vitreous luster and striations. They are translucent to transparent depending on depth of color. Crystals have a conchoidal fracture and are quite brittle, so collectors are careful with mounting. Hardness has been measured at ~4.5 (Mohs). Crystals occur as singles or sprays.  Most legrandite crystals are small and less than 1.0 to .5 cm in length. Like its zinc arsenate relatives, legrandite is a secondary mineral from the oxidized zone where zinc- and arsenic- bearing primary minerals provide the metallic cations.

Southwood and Megaw (2020) describe the Flor de Peña legrandite prismatic crystals as having blunt dome and pinacoid terminations and occurring “on a dull reddish-orange brown gossanous matrix of massive to botryoidal smithsonite.”   However, I am somewhat confused as to the matrix!  The matrix on my specimen is not a ferruginous gos

 

san and is more of botryoids composed of very tiny, sparkly green crystals.  There are several photos in MinDat that are similar to mine.  For example, Jordy Fabre states: “Nice miniature with prismatic crystals [legrandite] on Smithsonite matrix that we analyzed [green].”  Robert Lavinsky has a photo of: “gem legrandite crystal rosettes are very aesthetically clustered or isolated on the undulating, layered latticework of tiny sparkly, gemmy, dark olive-greenish sphalerite crystals.”  Paul de Bondt states: “Yellow legrandite crystals on dark green smithsonite.”  I simply cannot identify these small crystals. What I do recognize is that many collectors believe legrandite specimens from the Type Locality are quite rare.

Width of specimen ~9 mm.

Legrandite crystals on tiny green crystals (see text).  Width FOV ~7 mm.  Crystals are somewhat more yellow in real life.  Best the digital camera could do with vitreous crystals.

The most widely known legrandite specimens are from the Ojuela Mine at Mapimi, Durango, Mexico.  Southwood and Megaw (2020) noted that “Ojuela mine legrandite is commonly more gemmy, more lustrous, and more elongate with prominent sharp elongate dome terminations….Ojuela legrandites are widely considered as one of the ‘holy grails’ for collectors of Mexican, if not worldwide, minerals.”  But unfortunately, I do not have a holy grail Ojuela legrandite.

The Wulff-Pardo legrandite mounted on pedestal in Perky Box.  Height ~9 mm.

Now, I also have a second legrandite specimen, the Wulff-Pardo specimen that was collected at “Santa Eulalia.”  It is a single 9 mm. spray of tightly packed, single crystals each with a flat termination, all are striated and sort of a dull orange color. Here is the problem:  Southwood and Megaw (2020) note that the “Inglaterra Mine in the Santa Eulalia District …is the final Mexican legrandite locality, although the species is only known from five or six specimens collected here in 1986.”  I am convinced that the Wulff-Pardo specimen was collected before 1986!  Is this a seventh specimen, or is the locality information on this original Perky Box mislabeled?  That is one of life’s persistent questions and far above my pay grade for an answer.

Whoa, hold the press due to a serendipitous discovery! The Free Dictionary defines serendipitous as: making fortunate discoveries while searching for other things. The heirs of a CSMS members consigned a collection of rocks and minerals to Rebecca Nohe Estate Sales, a local firm that hosted a sale today.  I was hesitant about attending due to Covid-19; however, a limited number of potential buyers were allowed in at any one time for a 30 minute viewing/purchase (by appointments only) and masks were required of all persons entering the premises.  So off I go to see the goodies and what did I notice but a specimen of the holy grail!!  Yep, a legrandite specimen in the boxes contained a number of nicely terminated crystals from Mina La Ojuela, Mapimi, Durango, Mexico.  The specimen was originally purchased from the Mineral Adit Rock Shop in Colorado Springs for $60; however, I picked it up for $4.  It is not often that collectors can have a holy grail mineral for a nice four bucks.  Wow.  So now I have legrandite specimens from all three locations in Mexico and am happy as a lark! 

  

Several photomicrographs of legrandite crystals on botryoidal smithsonite and ferruginous gossan matrix.  Prismatic crystals range from ~.5 to 2 mm.

Another one of my favorite idioms: Why do people say happy as a lark?  It simply is derived from the birdsong of the lark. When you listen to the lark's birdsong, it sounds very happy, and thus the phrase "happy as a lark.". It connotes a sort of released abandon of happiness, fully embraced and unguarded.

LEARNING FROM ANTIMONY MINERALS

I AM STILL LEARNING      Michelangelo at age 87

I AM STILL LEARNING      Mike today

Antimony is one of those minerals that tends to ring a bell with people, but very few really know what it is, where it comes from, or how it is used!  Actually, antimony has been known for centuries and was being used as an eye cosmetic (mascara) by 3000 BC., and the most famous advocate might have been Jezebel whose exploits are recorded in the Hebrew Bible.  In her last earthly event before she was killed, Jezebel  “painted her face, and tired her head, and looked out at a window.” (2 Kings 9:30).   Early uses as a “medicine” evidently were for laxatives; however, antimony can be toxic and I would “prescribe” ExLax rather than powered antimony!  Today physicians may prescribe a form of antimony to “kill” nasty protozoans that have infested a person. Antimony is used widely in industry, mostly as a hardener in the manufacture of lead-acid batteries and ammunition (~40%).  It is also widely used in clothing as a fire retardant (~40%), glass, paint, and PET (polyethylene terephthalate) plastic bottles (PET beverage/water bottles should never be hearted) account for most of the remainder.  With our “throw away” culture all of those PET bottles containing antimony head to the landfill and may end up emitting toxic fumes (long term studies are inconclusive).

China is the world’s leading producer of antimony and in 2019 their mine production totaled 100,000 metric tons (out of 169,000 metric tons produced world-wide).  The other major producers were Russia, Tajikistan, Bolivia, and Turkey---countries not known for sterling environmental records. The United States has not mined antimony for several years; however, there are known reserves in Nevada, Utah, Idaho, Alaska, and Montana.  About 14% of our domestic use is obtained from recycling lead-acid batteries while the remainder (86%) is imported.  In 2018 antimony was added to the National Defense Stockpile of minerals. (Information above from U.S. Geological Survey, Mineral Commodity Summaries, January 2020).  

Stibnite, antimony sulfide [Sb₂S₃] is the major ore of antimony although some 200 or so other minerals contain the element.  A Posting describing stibnite may be found April 16, 2013.

I have a few of these “other” minerals containing antimony in my collection and four were described in past postings including cylindrite (January 23, 2017), cervantite (April 16, 2013), franckeite (February 26, 2020), and native antimony (April 16, 2013).  Four others, in my collection described below, include meneghinite, senarmontite, stibarsen, and gudmundite.

Senarmontite is an antimony oxide [Sb₂O₃] that often appears as nice octahedral crystals that at first glance could be confused with the octahedrons of magnetite.  However, senarmontite is not magnetic and has a color of gray to white or occasionally red to colorless.  The colorless variety is transparent while the others are translucent to mildly opaque.  Although my specimen is a nice octahedron, senarmontite also occurs as a massive and or granular mineral. Colorless crystals are subvitreous while others have a resinous luster, but all have a white streak.  The mineral also is quite soft at ~2 or a little more (Mohs).

The octahedron of translucent senarmontite.  Width/length crystal ~7 mm.     

My specimen is from the Djebel Hammimat Mine, Ain Babouche District, Oum el Bouaghi Province, Algeria, and I was unable to learn much about the mine except that it produced antimony from a variety of minerals including senarmontite. MinDat noted that senarmontite is a secondary mineral formed by oxidation of antimony, stibnite, and other antimony minerals in hydrothermal antimony-bearing deposits.

Stibarsen (AsSb) is a rather interesting mineral for several reasons.  The name comes from its composition of stibium (Latin name for antimony) and arsenic. It is one of those minerals that is composed of two metallic or semi-metallic elements (alloy-like).  In most minerals, metals or semi-metals form a positive charged cation (+), for example cuprite (copper oxide, Cu₂O).  However, I have posted on several Arsenide Group minerals where the arsenic serves as the negatively charged anion (always 3-) and combines with the positive metal cation: algodonite Cu₆As; domeykite Cu₃As; löllingite FeAs₂; skutterudite (Co,Ni)As₃. There are also similar Antimonide Group minerals where antimony serves as the negative charged anion (always 3-).  They are much rarer than arsenides and the only specimen in my collection is the silver antimonide dyscrasite Ag₃Sb.

MinDat refers to stibarsen as an antimonide with a formula of AsSb with both the antimony and arsenic having oxidation states of 3-(As) and 3- (Sb).  However, the ratio of arsenic and antimony seems to vary and other databases such as WebMineral use SbAs.  Then there is the discredited mineral allemonite floating around in the literature.  Actually, it was designated a synonym of stibarsen in 1982 when the IBM anointed stibarsen as the correct name.  However, readers might encounter allemonite as a descriptive term: allemonite I—greater content of antimony than arsenic; allemonite II—equal content of arsenic and antimony; allemonite III---greater content of arsenic than antimony.  And, so it goes.

The beautiful thing about learning is that nobody can take it away from you.  B.B. King

Stibarsen has a tin-white to gray to gray-white metallic luster and color with a gray-black streak.  It occurs as massive or a reniform (kidney-like) habit (often seen in hematite).  As a metal it is opaque and fairly soft at ~3-4.  It seems to form in lamellar, graphite-like sheets, is brittle and tarnishes to a dark gray.  As with arsenic, stibarsen puts out a garlic-like odor when struck. Stibarsen occurs in pegmatites and hydrothermal veins.

The graphite-like sheets of stibarsen.  Width FOV ~1.1 cm.

Reverse of above photomicrograph.  Lustrous, botryoidal typical stibarsen.  Width FOV ~1.1 cm.

My specimen, as do many stibarsen specimens on the market, came from the Engineer Gold Mine, Tagish Lake, Atlin Mining Division, British Columbia, Canada. The Mine and the District are well known for crystalized gold specimens and a “gold rush” to the area was contemporaneous with the more famous Klondike Gold Rush.  There is still exploration activity at the mine and an excellent summary of past mining and current work may be found at :  www.davidkjoyceminerals.com/pagefiles/articles_engineermine.asp

Gudmundite is an iron antimony sulfide, FeSbS, that has been collected from a number of localities but is best known in the mines of Bolivia and Slovakia.  I find it interesting that the iron arsenic sulfide, arsenopyrite (FeAsS), is a very common hypogene mineral, the oxidation of which accounts for a large portion of the arsenic found in secondary minerals, especially as the AsO₄ radical while gudmuntite is not a common mineral. Gudmondite, like other antimony minerals, has a metallic luster and a steel-gray to silver white color and will tarnish with exposure to “air.”.  It usually appears as a fine-grained crystalline mass with the crystals beyond the power of my scope.  It is opaque and will leave a gray black streak on unglazed porcelain. It is harder than stibarsen with ~5-6 (Mohs). 

Grainy, metallic gray crystals of gudmundite.  Width FOV ~1.6 cm.

My specimen of gudmundite came from the Pezinok Antimony Mine in the Male Karpaty Mountains, Slovakia. MinDat states “the mine is one of the largest hydrothermal antimony deposits in Slovakia. Small-scale mining of antimony started in 1790 and after some breaks finally stopped in 1991 for economic reasons.”  Many of the mines in the region also produced gold and electrum.  I cannot read Slovak nor Czech (the language of most of the professional articles) but Dill (1998 in English) noted that antimony mineralization in the Western Carpathian Mountains (i.e. Pezinok Mine) occurs in tectonic collision zones but unlike porphyry copper deposits, antimony deposits are distal relative to the subduction zone. They are confined to sections of the fold belt where the continental crust is thick and was subject to strong horizontal displacements. I found that one of life’s persistent questions and will continue reading!  

At last, an antimony mineral with an identifiable shape, and one collected from the U.S.—meneghinite, a lead copper antimony sulfide [Pb₁₃CuSb₇S₂₄] from the Red Bird Mine, Antelope Springs Mining District, Pershing County, Nevada—15 miles or so east of Lovelock.. The Red Bird was primarily a mercury mine and is well known for beautiful red crystals of the mercury sulfide, cinnabar (see Posting November 30, 2012). Secondary production included gold, silver, copper, lead, and antimony. According to the USGS (https://mrdata.usgs.gov/mrds/show-mrds.php?dep_id=10040308) The Red Bird was discovered in 1907 but did not produce until 1914 and then intermittingly after that until closing shop in 1949.  The disseminated cinnabar was hosted in Mesozoic (Triassic and Jurassic) carbonates, especially in fracture zones. Evidently these veins were emplaced during the Miocene as a result of extensional magmatism (Noble and others, 1988).  That is, Miocene extensional tectonics involved the stretching of the earth’s crust producing what we know today as the Basin and Range physiographic province.

Prismatic, metallic crystals of meneghinite, stacked in mass.  Width FOV ~1.2 cm.

Above two photomicrographs of meneghinite in and on a quartz matrix.  Width FOV 1.2 cm. 

Meneghinite has the metallic luster and blackish-gray or lead-gray color of other lead and antimony minerals.  It often occurs, as in my specimen, as striated acicular or prismatic crystals (long and slender) that are quite brittle.  The mineral is opaque, leaves a shining metallic black streak, and is quite soft (~2.5 Mohs). As noted above, it occurs in hydrothermal veins associated with many other metallic minerals. At some localities, bismuth may replace some of the antimony and copper content is variable.  About the only way I could visually identify meneghinite (maybe) is to know about the collecting mine!

Learning is a treasure that will follow its owner everywhere. Chinese Proverb

 REFERENCES CITED

Dill, H., 1998, Evolution of Sb mineralisation in modern fold belts: a comparison of the Sb mineralisation in the Central Andes (Bolivia) and the Western Carpathians (Slovakia): Mineralium Deposita. Vol. 33.

Noble, D.C., J.K. McCormack, E.H McKee, M.L. Silberman, and A.B. Wallace, A.B., 1988, Time of Mineralization in the Evolution of the McDermitt Caldera Complex, Nevada-Oregon, and the Relation of Middle Miocene Mineralization in the Northern Great Basin to Coeval Regional Basaltic Magmatic Activity: Economic Geology, v. 83.