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.