Davyne - Encyclopedia

DAVYNE

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Hexagonal
    Chemistry : (Na,Ca,K)8Al6Si6O24(Cl,SO4,CO3)2-3
    Rarity : Very rare

Davyne is an extremely rare mineral from leucite lavas, very deficient in silica, which is also found in the ejecta of Italian volcanoes. Davyne belongs to the cancrinite group, of which it designates the chlorinated terms, the carbonated terms constituting cancrinite in the strict sense. It was named in honor of the English chemist Sir Humphrey Davy who described certain chemical elements. Davyne occurs as colorless to white, vertically streaked, hexagonal prismatic crystals associated with nepheline and leucite, as well as vesuvianite and scapolite in volcanic ejecta.

Main photo : Davyne from Mount Somma, Naples, Italy © Matteo Chinellato

Davyne from Brenk, Brohltal, Ahrweiler, Germany © Volker Betz
Davyne from Vesuvius, Naples, Italy © Italo Campostrini
Davyne from Ettringen, Germany © Stephan Wolfsried
Davyne from Vesuvius, Naples, Italy © Enrico Bonacina

Davyne in the World

Superb 4 cm crystals, the best known, come from the ejecta of Somma and Vesuvius (Italy). Davyne is also known at Pitigliano (Tuscany), in blocks of metamorphosed limestone packed in pumice deposits, and in the leucite lavas of the island of St. John (or Zebirget) in the Egyptian Red Sea, a site famous for its extraordinary gemmy peridot crystals. It is also reported in numerous German volcanic deposits (Brenk, Mendig, Wingertsberg, Kruft, Ettringen, etc...).

Davyne in France

Davyne is not present in the French underground.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 5.5 to 6
Density : 2.42 to 2.53
Fracture : Irregular to conchoidal
Streak : White

TP : Translucent to transparent
RI : 1.515 to 1.522
Birefringence : 0,004
Optical character : Uniaxial +
Pleochroism : None
Fluorescence : None

Solubility : Acids


Magnetism : None
Radioactivity : None

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