Detail Whole Slab
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Oil slate

The close-up view of each stone type shows a relatively true image of the crystalline structure and the colouring. This is suitable for grained slabs to a limited extend only. In regard to the colour matching, please take an original sample of the stone from your furniture store as a basis.

The standard version we use for our table tops is the rough-cleaved surface showing the natural fracture pattern of the split up layer with is coffee-brown color. The raw surface can be supplied too when desired. It is the highest layer of the processable seam and exhibits often stored fossil fragments of the petrified sea animals with its clearly brighter colour.


Holzmaden Posidonian slate, a black, thin plated, bituminous sedimentary rock, finely arranged in parallels and dating from the Lias formation (Jurassic period) is one of the most famous in the entire natural stone trade. It is remarkably homogeneous with regular grains and without patterns. Certain strata are enriched with large numbers of fossils - especially mussels of the type posidonia, along with ammonites, fish, as well as remains of amphibians and reptiles. 


In the Lower Jurassic period, extensive areas of Germany were covered by a relatively shallow sea. At its deeper reaches, it was only very inadequately aerated and the supply of oxygen was drastically reduced. During the period, an euxenite environment prevailed, in which bituminous clays and mud formed and settled. In the Holzmaden slate quarries of the Holzmaden posidonian slate, excellently preserved fossils were found, and are still found. 

Hardness Soft Stone
Structure Type Homogeneous Structure
Synonyms Holzmadener Schiefer, Jura Ölschiefer
Group Sediment Rock
Petrographic Assignment Slate clay, Oil slate
Age 160 million years (Lias Epsilon, lower Jurassic period)
Colouring Minerals Brown carbonate, black-brown bitumen, clay minerals, mica
Average Hardness 3 (according to Mohs's hardness scale 1-10) / Soft stone
Deposit Germany, Baden - Wuertemberg, near the communities Holzmaden, Ohmden, Zell and Bad Boll