Assertion: obsidian | /r/HasAspect | a hardness of 5 - 5.5
Facets:
value: on the mohs scale
type: OTHER
Source sentences:
text: Although obsidian has a hardness of 5 - 5.5 on the Mohs scale, which is softer than quartz, it is a durable material.
text: However, quartz is a harder material than obsidian, at 7 on the Mohs scale, whereas obsidian has a hardness of 5 to 5.5.