Show Summary Details

Quick Reference

1 Chalcedonic (see chalcedony) variety of cryptocrystalline silica, SiO2, that occurs as nodules or irregular masses in a sedimentary environment, often in association with black shales and spilites.

2 A fine-grained rock consisting of beds of cryptocrystalline silica, usually of biogenic, volcanogenic, or diagenetic (see diagenesis) origin.

Subjects: Science and Mathematics.

Reference entries

See all related reference entries in Oxford Index »

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.