Translation of "Chert" into Welsh

(geology, uncountable) Massive generally dull colored and usually opaque quartzite or hornstone or impure chalcedony or other flint-like mineral. By general usage in mineralogy and geology, a chert does not have a conchoidal fracture. In North American archeology the term chert occasionally is still used for various siliceous minerals (including flint) that have a conchoidal fracture; this leads to confusion between the terms flint and chert in some archeology texts. [..]