Bonacker quarry, Gedern, Vogelsberg, Germany

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Who says Gedern, also says Erionit-Offretit.... Erionit-Offretit is found here in a lot of forms, usually tightly intergrown together, with very nice Chabazit, Phillipsit, Thomsonit, Gismondin, Levyn, Calcit, Montmorillonit and Aragonit.
We walked around the quarry (which has changed a lot since 2000... in the burning hot sun. So hot we had to stop working on the hard basalt after 2 hours... You have to look for black Basalt with a brownish teint, brown spots in it. Usually that rock has a lot of cavities with unweathered Erionit-Offretit, grown on Levyn-xls, on which usually a lot of Chabazit and Phillipsit is grown. It was our luck that the quarry had just dynamited a part of the quarry so there was a lot of fresh material lying around with a lot of cavities just waiting... Very attractive material. All micromount material because the xls usually don't exceed 2-3 mm. But we found cavities now (and in earlier years) of 15 cm large...

We've visited Gedern six times in 1990, 1998, 1999 and 2000 in official excursion by the Gea etc, and... in mai 2005, and...

Click on the thumbnail for a panorama of the quarry march 2007 for the last time:

You can say there are two types of rock here. -a black, very hard, massive Basalt, containing few cavities. In those cavities of course Chabazit, Phillipsit, much Calcit and Montmorrilonit/Smectit (often covering the Zeolithes) but rarely also Aragonit:

-and a brownish, relatively soft, Basalt, containing a lot of cavities. In those cavities you can find the other minerals like the Thomsonit below:

We have now about 300 micromounts of Gedern... there's a lot of beautiful stuff to photograph...

If you're searching for mineralogical articles (Betz V, Hentschel G - 1978 - 'Offretit und Erionit von Gedern (Vogelsberg)' Geol.Jahrbuch Hessen 106 419-421 ; G. Gottardi and E. Galli, Natural Zeolites, Berlin ; New York : Springer-Verlag, 1985, etc...) on this locality, please contact us...

Read more in the below Pdf-fed article on Gedern:
- 1997-mm-amsterdam on Vogelsberg in general (3.360 Kb)

Also see: on the Offretit-Erionit-Levyn intergrowths!,, volker betz, on this location.

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