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
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.
small vug in Limburgite from Quarry I, with Phillipsite coating aggregates of Montmorillonite.
Field of view about 20 mm
|Augite crystal , 5 mm long with weathered Olivine .||Augite twin. Field of view about 7 mm.|
|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.|
|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.|
|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.|
|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|