What does conchoidal mean in mineralogy ?
Fracture : definition
This term designates a fracture with the formation of more or less marked curved rupture planes, evoking the growth streaks present on the shells of bivalves, hence its name. It is characteristic of quartz, obsidian or opal (photo on the right).
A sub-conchoidal break has the same characteristics but with less marked curved break planes.
A sub-conchoidal break has the same characteristics but with less marked curved break planes.