Paragenesis and sucession of the minerals at Limberg bei Sasbach, Kaiserstuhl, Baden (Germany) 

The Limburgite rock is in parts very porous and contains enormous numbers of vugs of various shape and size. Some are spherical but most are irregular shaped in sizes from a few mm to 10 cm  and may be larger.  The  Limburgite rock matrix consists of many idomorph  Augite  crystals up to two centimeters, embedded in a glass matrix and yellow brown mostly altered Olivine. The Olivine shows sometimes small idomorph crystals, and was first collected by Walchner in 1819, and subsequent (1823) described as a new  mineral species "Hyalosiderite", based on crystal shape and gravimetric analysis. Today  it is considered as an altered variety of  Fe-rich Olivine.  The walls of the vugs are partially covered with an amourphous silica coating which was named "Kieselsäurehydrogel" by Lorent (1933). Coated Augite crystals and often visible on the sorface of the vugs. The amorphus coting is folllowed by Montmorillionite of various colours and by a sequenze of Zeolites in the order: Offretite, Phillipste (spheres),  Faujasite, Phillipsite as Crystals and Cabazite. Small droplets of  Opal may also be present nucleating on offretite resulting in "sea-urchin" like forms. Crusts  and hemispheres of Calcite are common, but crystals are rare and etched.  A second mineral paragenesis at Limberg is that of Calcite, Haylite and  Aragonite which is mostly present in fissures and in vugs of a tuff found in quarry VII.  Lorent (1933) shows a picture with a vug of 15 cm.











Home A small vug in Limburgite from Quarry I,  with  Phillipsite coating aggregates of Montmorillonite.
Field of view about 20 mm

Augit_1 Augit_Zwilling
Augite crystal , 5 mm long with weathered Olivine .  Augite twin. Field of view about 7 mm.
Olivin Olivin_zeichnung
A Crystal of "Hyalosiderite " (weatherd Olivine) an its correspondig crystal drawing.
Field of view about 3.5 mm.
Surface layer of a limburgite boulder on which Augite and Olivine are concentraded. Vugs (white) are coated with Phillipsite. Specimen of 6x7 cm.
 Augite-Crystal embedded in a mixture of  altered Olivine.
Crystal is 10 mm long.
Augite-twin. Field of view is 8 mm.
mont_fau Miont_off
Mont_phill Hyalite_mont
Unknown dentritic aggregates partially covered with Phillipsite.
 Field of viewabout 5 mm.
Opal spheres nucelating on radial aggragates of Offretite. From Quarry II.  Field of view about 0.8 mm.
Faujasit_pol1 Pol2
Faujasite and Phillipsite in transmitted polarized light. Left with parallel Nicols , right with crossed Nicols.  The regular Faujasite shows no effect, while the radiating Phillipsite show a "Brewsters cross"visible though the Faujasite. Field of view about 1.5  mm.
Phillipsit_radial Phill_Fau
Radiating aggregate of Phillipsite nucleating from a unknown center.
 Field of view aboput 2 mm
Faujasit on Phillipsite with brown Limonite. Filed of view abou2 mm
The Limberg at The Limberg as a Geotope  with a map The Limberg for tourists
© Volker Betz (2010)  All rights reserved.