NAGRA Opalinus Clay (…002 - Version 1
FEP 12.1.10 Calcite veins

Precipitated calcite coating is often observed within water-conducting features (calcite veins), affecting the hydraulic and geochemical properties of these features. Indeed, the presence of such a coating is evidence that the feature conducts (or has at some time conducted) flowing water. Only minor calcite precipitation was observed in the Opalinus Clay, giving strong palaeohydrogeological evidence for the long-lasting absence of flowing water.