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Litchfieldite is a rare igneous rock which is coarse-grained, foliated and a variety of nepheline syenite, sometimes also called as nepheline syenite gneiss or gneissic nepeheline syenite
From its occurrence at Litchfield, Maine, USA
Durable Rock, Medium Hardness Rock
Coarse Grained Rock, Opaque Rock
Argillites are highly compact sedimentary or slightly metamorphosed rocks that consist largely or wholly of particles of clay or silt but lack the fissility of shale or the cleavage characteristic of slate
From Latin Argilla (clay) and -ite in English which became agrilla+ -ite = Argillite
Fine Grained Rock, Opaque Rock