HYDROBASALUMINITE: A NEW ...
HYDROBASALUMINITE: A NEW OCCURRENCE IN BELGIUM
E. GoemaereGeologica Belgica - Volume 7 (1-2) - 2004
ABSTRACT.
We report the first Belgian occurrence of hydrobasaluminite as a weathering product in the waste deposits of an old mined coal seam. Basaluminite was identified after ‘natural’ laboratory dehydration. A description of the depositional setting and the mineralogy together with a brief discussion about the origin of this hydrated aluminium sulphate mineral is presented.
KEYWORDS: hydrobasaluminite, basaluminite, Westphalian, coal seam, weathering, X-ray diffraction, Liège.
Photo 1: partial view of the mineralised pocket.
a) black shales at the top of the mined Bomebac coal seam shales noirs.
b) wastes deposit with black shales and impure coal.
c) iron hydroxydes stained material and
d) hydrobasaluminite (white patches) and mixture of hydrobasaluminite and allophane (yellow patches).
The compass gives the scale.
Photo 2: complex layered and zoned structure of a pocket sample.
Photo taken 36 hours after sampling.
Fracturation related to the partial dehydration of the hydrobasalumite to basaluminite affects coherence of the material.
e) allophane. goethite and iron hydroxydes.
f) partial dehydration of hydrobasaluminite.
g) pure allophane layer (corn color).
h) microlayering.
Photo 3: naturally dehydrated allophane with a conchoidal fracture. Dehydration induces irregular fractures in the sample– SEM (IRScNB) – unpublished photo
Photo 4: inframicrometric globules of allophane – SEM (IRScNB) – unpublished photo
