Assertion: amber's hardness | /r/HasProperty | refractive index of 1.5–1.6
Facets:
Source sentences:
text: Most amber has a hardness between 2.0 and 2.5 on the Mohs scale, a refractive index of 1.5–1.6, a specific gravity between 1.06 and 1.10, and a melting point of 250–300 °C.