BIRDS OF A FEATHER: CARMINITE AND ARSENIOSIDERITE

There is not much info that I could locate about mining at Benjamin Hill in Sonora, Mexico.  Evidently Wm. Panczner noted the locality in his 1986 Minerals of Mexico; however, I could not locate a copy. I do have a copy of the 2011 edition of Minerals of Mexico distributed by MineraliA; but, no luck here either.  MinDat simply listed the presence of copper as a mineral commodity with the occurrence of the arsenates arseniosiderite, beudantite, carminite, sewardite, and the zinc (with minor iron) sulfide, sphalerite.

A few years ago, at a dusty small rock/mineral shop in Arizona, I nabbed a perky box containing carminite [PbFe₂(AsO₄)₂(OH)₂ ], one of those nifty minerals with a metal cation or two plus the arsenate anion with a hydroxyl stuck on the end.  Most of these arsenates are quite colorful and I have described many in this Blog.  Carminite is an oxidation product of arsenopyrite [FeAsS] that is so common in sulfide ore deposits.  The lead was derived from the oxidation of sphalerite, a zinc-iron sulfide.

Carminite gets its name from the carmine- to terra-cotta red color, resulting I presume, from the weathering of iron. Crystals have a vitreous luster, are translucent and soft (~3,5 Mohs), brittle, and with a mostly red streak. Large crystals are lath-like, flattened, and elongated, although some crystals are acicular tuffs.  Then there are the crystals in my specimen:  really, really, small and somewhat indistinguishable with the scale I can produce; however, some are definite laths. There have been concerns that sewardite, the calcium analogue (replaces lead) of carminite, might be mistaken for carminite—or vice versa! MinDat noted “both sewardite and carminite seem to occur at the Benjamin Hill locality. A sample sold as "sewardite" at the 2007 Munich show turned out to be an intermediate, but most probably Pb-dominant solid-solution member (U. Kolitsch, unpubl. data).”  Carminite and sewardite would be difficult for me to visibly distinguish however, I am going with the more common carminite although both could be present on the same specimen.

Photomicrographs of small (less than .5 mm) crystals/grains of red carminite and gold-yellow arseniosiderite.  The large carminite lath in the lower photo is ~.5 mm.  I presume the quartz is the clear to white material.

In the last Posting I was fond of using idioms in the verbiage and blamed the usage on “boredom” in my self-quarantine.  One international reader sent an email stating that he/she did not quite understand idioms.  OK, sorry about that mistake for English idioms are often difficult for a non-native speaker to understand.

Theidioms.com explain that an idiom is a phrase, saying or a group of words that has a metaphorical (not literal) meaning, which has become accepted in common usage. An idiom's symbolic sense is quite different from the literal meaning or definition of the words of which it is made. There are a large number of Idioms and they are used very commonly in all languages. There are estimated to be at least 25,000 idiomatic expressions in the English language [and I commonly use them in everyday language.]  So, let me try again.

The Arsenate minerals, those with the metal cation(s) plus the AsO₄ anion, often are found with one another.  If your specimen has one arsenate mineral present, there are usually additional arsenates hanging around.  So, carminite is often found with arseniosiderite and I would state that birds of a feather often flock together meaning that since both are similar arsenates they might occur together in your specimen.

This proverb has been in use since at least the mid-16th century. In 1545 William Turner used a version of it in his papist satire The Rescuing of Romish Fox:

Byrdes of on kynde and color flok and flye allwayes together [credit: phrases.org.uk].

Now for the English speakers: Es geht um die Wurst. Translation: It's about the sausage.  Would you understand that German idiom?  Well, it means it’s now or never!

As noted, the arsenate arseniosiderite [Ca₂Fe₃(AsO₄)₃O₂-3H₂O] is a common associate of carminite.  Most specimens that I have seen are gold to yellow to yellowish-brown to reddish-brown although black and brown crystals have been report.  I assume the various colors are associated with the amount and type of iron oxide present. Good crystals are rare and granular masses are common (as in my specimen) although flattened fibers and radial aggregates are common.  The mineral is opaque, harder than carminite (~4.5 Mohs), has a greasy/silky luster, and a yellow streak.  As with carminite, arseniosiderite results from the oxidation of other arsenic-bearing minerals such as arsenopyrite and perhaps scorodite.

Sich auf die Socken machen. I will even translate: To make the socks.

Well that German idiom means to make tracks out of here!