R878 Sample ID R878 • Cabinet B Rhyolite "thunder egg" 9cm W x 5.9cm H x 4.2cm D • 238g Sample TypeRockRock QualityIgneousRock TypeExtrusive CompositionFelsicTextureColor IndexReddish Clast SizeAcid ReactionMohs Hardness 7 Rough light and dark exterior, polished smooth glassy reddish brown interior sphere with white at the center. Description of Mohs scale here