Cumberlandite

Historical records reveal that it was smelted as early as 1703, and it was used in forging cannons during significant events such as the Siege of Louisbourg in 1745 and possibly the American Revolutionary War.

Its unique origin, distinct appearance, and ease of identification contributed to its selection as the Rhode Island state rock.

Cumberlandite is an uncommon mafic igneous rock known as a melanocratic troctolite, or by IUGS classification, titaniferous magnetite melatroctolite.

[8] Bulk rock geochemistry shows the below analysis with trace Pb: Troctolites are unusual olivine-rich pyroxene-poor gabbros common in layered mafic intrusions believed to have formed as cumulates in a magma chamber.

Cumberlandite has light phenocrysts of labradorite in a dark, fine to medium-grained matrix of magnetite, ilmenite, olivine, and hercynite spinel.