Pyrite crystals in clay (Falcacci stope, Rio Marina, Elba Island, Tuscany, ItalyLast Updated: 3rd Jan 2014
By Giuliano Bettini
A typical finding in the Falcacci stope was (or still is ...) Pyrite crystals confined in the clay.
Here I show some specimens I found in the 90'.
In Ref. Orlandi, P., & Pezzotta, F. (1997). Minerali dell'Isola d'Elba. Edizioni Novecento Grafico, Bergamo, the authors write:
“Falcacci: in questo cantiere si rinvennero cristalli di Pirite riuniti in gruppi anche di ragguardevoli dimensioni, immersi nel materiale argilloso verdastro, con cristallizzazioni che comprendono il cubo, il pentagonododecaedro e l’ottaedro. Tali forme possono apparire singole o in combinazione tra loro, spesso in associazione con faccette di forme più rare che ne smussano gli spigoli.”
ie, freely translated:
"Falcacci: in this site were found Pyrite crystals also gathered in groups of considerable size, surrounded by greenish clay material, with crystallization which include the cube, the octahedron and the pyritohedron. These forms may appear single or in combination between them, often in association with small faces at the edges ."
In fact, I found small single crystals in a yellowish clay. In a “greenish clay material” I found Sphalerite.
In the following pictures I show:
- a sample of yellowish clay with Pyrite crystals inside;
- Pyrite crystals, found from washing of about a 10x10x10cm block of clay;
- imperfect crystals, crystal aggregates or twinned crystals. That’s what is most frequently found;
- small but perfectly formed Pyrite crystals washed from clay. (The perfect crystals are quite rare);
- examples of typical crystal faces at Falcacci, and some other rare faces I found.
Crystal faces: cube (100), octahedron(111), diploid (213), pyritohedron (102).
The example crystals were constructed using a Software for crystal drawing: cube (red), octahedron (green), diploid (blue), pyritohedron (azure);
- other pictures from my Galleries.
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