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Ignimbrite is a volcanic rock consisting mainly of pumice fragments, formed by the consolidation of material deposited by pyroclastic flows
From Latin ignis fire + imber, imbr- shower of rain, storm cloud + -ite
Durable Rock, Medium Hardness Rock
Fine Grained Rock, Opaque Rock
Lignite is a soft brownish coal which shows traces of plants and is intermediate between bituminous coal and peat
From French, Latin lignum wood + -ite1
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock