ITALIAN ANTIMONY AND BORON BUT NO COINS IN A FOUNTAIN

 

One of the problems for an ole plugger like me is to purchase a very small collection, 10 or a dozen specimens, and then decide that a few of the minerals may be too complicated (especially too small) to describe on this Blog. Most of the time these minerals are not in my meager mineralogical vocabulary and are often from non-North/South American mines. It is then that I thank the existence of MinDat!

Two recent specimens are from mines in Italy, and I have spent several hours trying to learn something about the mines and their minerals. I suppose that is the meaning of being a lifelong learner!

The Le Cetine di Cotorniano Mine, Chiusdino, Siena Province, Tuscany, Italy, is a closed antimony mine that only lasted for a couple of years in the mid-1940s. I tried to locate something about the history of the mine but since I do not read Italian, I was in a bind. What was interesting, at least to me, was that the mine operated right at the end of WWII (1943-1945). Was the antimony used in the “war effort” and was the mine discarded with the capitulation of German and Italian fascists holding the northern part of the country? I don’t know.

Dark, elongated stibnite crystals (submillimeter in length), the major source of antimony at the Mine. 

Yellow to yellow tan tripuhyite. Top crystal cluster is submillimeter in length as is the lower massive (with a few crystals) aggregate.

What I do know is that this small, obscure mine, at least to me, has a modern inventory of 83 valid minerals including five Types. Four of these five Types have antimony in various oxidation states. The specimen I purchased is tripuhyite [FeSbO₄], an antimonate (a metal; ferric iron 3+), oxygen (2-), and antimony with an oxidation state of 5+. Crystals are mostly composed of fibers that range from washed out yellow to brownish yellow to brown to brownish black. At times the fibers appear as a “mass of worms” while other specimens exhibit rosettes of fibers/crystals. The Clara Mine in Germany has produced some beautiful “blooming” rosettes and spherical crystal aggregates. The luster is usually dull to waxy, and someone has measured the hardness as ~6-7 (Mohs). 

The vug containing several minerals. Maximum width of vug ~3 mm. The yellow mystery mineral occupying most of the vug may be ?jarosite (see below).

My tripuhyite specimens occur within a vug from the mine matrix and are extremely small with individual crystals less than one mm. The mystery mineral that occupies most of the vug, well it is a mystery! The older label from Minerals Unlimited stated calcite; however, it is not a carbonate. My best guess is a few larger amber crystals are elpasolite [K₂NaAlF₆] while the majority of the smaller vitreous crystals are jarosite [KFe³⁺₃(SO₄)₂(OH)₆]. Due to the “smallness” of the crystals I cannot obtain good photos. I have identified a few stibnite crystals [orthorhombic Sb₂S₃] and a bright crimson dimorph of stibnite called metastibnite [amorphous Sb₂S₃].  There are tiny, numerous, scattered, acicular crystals that could be cetineite [(K,Na)₆Sb³⁺₁₂(Sb³⁺S₃)₂O₁₈(OH)_0.5 ·5H₂O] but I would need an electronic gizmo to give me some ID help. There are also other unknown minerals in the small vug!

Are these amber crystals elpasolite? Again they are submillimeter in size.

Bright crimson metastibnite. It evidently forms from the oxidation of stibnite, its crystalline dimorph. I am uncertain about the hexagonal stack of crystals.

MinDat (retrieved 23 August 2023) stated “Mineralization in brecciated dolomitic limestones developed in Triassic evaporitic deposits which has been silicified by hydrothermal fluids circulating in the fault system. These fluids deposited the stibnite mineralization.”

My second Italian Mine is the Brosso Mine located within the city of Turin. The mines have been known since ancient times for the abundance and great variety of their minerals, of which samples exist in all the collections of Europe. The beginning of the cultivation of these mines dates back, according to the news reported in the "Monograph of the Sclopis brothers", to the time of the Romans, who apparently practiced lead and silver metallurgy starting from the argentiferous galena. [Translated from comunee.Brosso.to.it;  Miniere di Brosso.]

By the 18^th Century miners were after pyrite to produce iron II sulfate [FeSO₄-xH₂O] that was used in the textile industry to fix various dyes and to blacken leather. By the late 1800s industry was distilling Brosso pyrite to produce sulfuric acid [H₂SO₄]. Although tough to find these days, Brosso collectors cherish specimens of pyrite crystals mixed with magnetite crystals.

As a small sidenote, starting about in the 5^th Century ferrous sulfate was mixed with tannic acids (from plants) to produce writing, and later, printing inks.

After the pyrite mining was abandoned, and perhaps in the 1960s, the Brosso was “reopened” as a specimen mine for fine minerals that had formed between the zone where intrusive igneous monzonite and marbles had become interbedded in mica schists. Mineralization, especially of secondary boron minerals, occurred between szaibelyite and ludwigite where they came into contact with each other inside the magnetite skarns (Ferris and others, 1978 and Giussani and Vighi, 1964).

The Brosso has produced, according to MinDat, 108 different minerals including one type specimen (the boron mineral canavesite). The thumbnail specimen I have is composed of magnetite, a little pyrite, and szaibelyite, an anhydrous magnesium borate [MgBO₂(OH)]. The latter is mostly found in boron-bearing skarn limestones and dolomitic marbles, or in evaporitic deposits where it is an alteration product of boron minerals like inyoite and colemanite; more rare in banded iron formations and serpentinites.

Black magnetite with white and buff fibers/lathes of szaibelyite. Width FOV ~7 mm.

Szaibelyite occurs as flatted fibers or lathes often as aggregates. Interestingly these fibers are inflexible and have a conchoidal fracture. They are white to buff in color, have a luster of dull to silky, and are soft (~3.5 Mohs). It is not the most handsome mineral in the cabinet but come from a quite historic and famous mine and ended up in the collection of Mineralogical Research Company before my purchase.

REFERENCES CITED

Ferraris, G., M. Franchini-Angela, 1978, Canavesite, A New Carboborate Mineral from Brosso, Italy: Canadian Mineralogist, Vol.16.

Giussani, A., L. Vighi, 1964: Caratteristiche e genesi dei minerali di boro, ludwigite, ferroludwigite, szaibelyite, camsdellite della miniera di Brosso (Ivrea). Periodico di Mineralogia, 33. Translated to: Characteristics and genesis of the ores of boron, ludwigite, ferroludwigite, szaibelyite, camsdellite of the Brosso mine (Ivrea). Mineralogy Periodical, 33.

AS for the coins in the Trevi Fountain:

The myth, originating in 1954 with the movie "Three Coins in the Fountain," goes like this:

• If you throw one coin: you will return to Rome.
• If you throw two coins: you will fall in love with an attractive Italian.
• If you throw three coins: you will marry the person that you met.

In order to achieve the desired effect, you should throw the coin with your right hand over your left shoulder.

An interesting statistic is that approximately a million euros worth of coins are taken from the fountain each year. Since 2007 this money has been used to support good causes.