Stones can have many aliases. This is due to language differences, supplier choice, coloquial trends or slang, or sometimes errors and ambiguity between rocks. Read more here.
|Black Marquina, Negro Bilbao, Spanisch Schwarz|
Commercial classification sometimes differs to the scientific, geological designation. In particular, some limestones are deemed marble especially if they take a high polish. Read more here.
|Petrographic assignment||Sedimentary limestone|
|Age||330 million years (Carbonic)|
|Colouring minerals:||White calcite coloured black by bitumen|
MOHS is the standard scale of hardness for minerals 1-10, with 10 being the MOHS of diamond. We also use the broad terms Hard and Soft for simplicity. Read more here.
A black limestone of the Carboniferous period with white calcite veins and fossil fragments (rudistes and corals), found north of Bilbao/Marquina in Spain
Called a marble commercially as it takes a high polish.
Also available in standard tile formats.
Petrology:Dense black limestone crossed irregularly by white calcite veins. Different wide cracks were generated by tectonic faults, filled by circulating solutions in the form of calcite. As the pigments (Organic carbon) did not dissolve, the veins remained white and formed an extreme colour contrast. Fossils fractures are no longer visible. Nero Marquina belongs to the bituminous lime as it contains black minerals like carbon or bitumen (Generated from sludge).
Petrogenesis:Black limestone was generated in estuaries of the sea near the coast (brackish water area) with bad ventilation but with a large growth of plants and plankton. Dead plants and animals did not decompose due to the low oxygen content but were covered by clay and lime sediments. Bituminous materials were generated under pressure and high temperatures causing the black colouring of the rock. In the case of extreme enrichment of such organic material this geo-chemical process can lead to oil forming.