Database of luminescent minerals 

Exotzamite

Chemical formula: See Buchite

Family: Rock

Status:

Display mineral: NON

Luminescence:

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Phosphorescence (in the common sense of the term) observable with the naked eye:

No data

Comments:

An uncommon metamorphic rock type composed mostly of glass, formed by the melting of a sedimentary rock or soil by heat from an adjacent lava flow or scoria eruption, or the burning of an underground coal bed. Buchite is a product of a special type of metamorphism, called pyrometamorphism (contact type, high to very high temperature, low pressure, often connected with coal fires). The primary description of buchite is a transformed or glassy sandstones associated with basalts (in Germany). Buchite is named for German mineralogist Baron Christian L. von Buch, who died in 1853. (mindat.org)

Even though they have different petrogenesis and petrographic characteristics from classic buchites, siliciclastic sedimentary rocks vitrified by volcanic activity, are misleadingly termed buchites. True buchites are siliciclastic sedimentary rocks that have been affected by metamorphism in the contact aureoles between basalt intrusions and solid sedimentary rocks. This mode of genesis is clearly different from isolated pyro-metamorphosed, siliciclastic uppermost crustal xenoliths with external glassy rims. In buchites, where glass is present, it occurs within the matrix of the rocks, whereas in the isolated siliciclastic xenoliths glass occurs mainly as external glassy rims. The differences in the nature and genesis of buchites sensu strictu and pyro-metamorphic, glass coated  from the West Eifel Volcanic Field, requires a distinct name that distinguishes between the two lithologies. Glass-coated pyro-metamorphic xenoliths are thus defined as Exotzamit. Buchites and exotzamites are products of metamorphism, the former by contact-metamorphism and the later by pyro-metamorphism within the magma. (Contact aureole-Buchite (Klipstein 1827) sensu stricto vs. Exotzamit nom. nov. – a new name for pyro-metamorphosed, siliciclastic crustal xenoliths with external glassy rims, Jan Bohatý, 2016)

Activator(s) and spectrum:

No spectrum yet

Best localities for fluorescence (*):

• Emmelberg, Eifel Mts., Germany;

(*)The data are not exhaustive and are limited to a few remarkable localities for fluorescence

Bibliographic reference for luminescence:

Reference for luminescence on the Internet:

Mineralogical reference on the Internet:

  http://www.mindat.org/show.php?name=Exotzamite

  http://webmineral.com/data/Exotzamite.shtml

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