cumberlandite (RIDZc;0)

cumberlandite

The designated state rock of Rhode Island. Black, medium-grained, porphyritic melatroctolite (phenocrysts of plagioclase), composed of magnetite, ilmenite, olivine, plagioclase, and accessory hercynite spinel; secondary chlorite and saussurite. Abundance of magnetite and ilmenite (up to 70% of rock) results in characteristic high specific gravity. The rock is massive, but locally exhibits a flow lamination caused by the planar orientation of plagioclase laths.

State	Rhode Island
Name	cumberlandite
Geologic age	Late Proterozoic? to Devonian?
Lithologic constituents	Major Igneous > Plutonic > Gabbroic > Gabbro > TroctoliteThe designated state rock of Rhode Island. Black, medium-grained, porphyritic melatroctolite (phenocrysts of plagioclase), composed of magnetite, ilmenite, olivine, plagioclase, and accessory hercynite spinel; secondary chlorite and saussurite. Abundance of magnetite and ilmenite (up to 70% of rock) results in characteristic high specific gravity. The rock is massive, but locally exhibits a flow lamination caused by the planar orientation of plagioclase laths.
Comments	Part of Esmond-Dedham Subterrane (West Bay Area)
References	Hermes, O.D. (comp.), Gromet, L.P. (comp.), Murray, D.P. (comp.), Hamidzada, N.A., Skehan, J.W., and Mosher, S., 1994, Bedrock geologic map of Rhode Island: Rhode Island Map Series No. 1, Kingston, Rhode Island, scale 1:100,000.
NGMDB product	NGMDB product page for 19719
Counties	Providence

cumberlandite

Hermes, O.D. (comp.), Gromet, L.P. (comp.), Murray, D.P. (comp.), Hamidzada, N.A., Skehan, J.W., and Mosher, S., 1994, Bedrock geologic map of Rhode Island: Rhode Island Map Series No. 1, Kingston, Rhode Island, scale 1:100,000.