(mineralogy) A soft, compact variety of talc, being an altered pyroxene, sometimes worked in a lathe into inkstands and other articles, found in New York and Canada.
1840, https://books.google.co.uk/books?id=OrqB7elAQrwC&pg=PA321&lpg=PA321&dq=%22rensselaerite%22&source=bl&ots=pj8PiIHqLW&sig=TtiKA3EELWApIeKjjdL3aE3kX0E&hl=en&sa=X&ved=0ahUKEwjfx4SR_p7TAhULD8AKHfJxAOA4FBDoAQhAMAk#v=onepage&q=%22rensselaerite%22&f=false ("Assembly: State of New York, Issue 50", published 1840, digitised 2010).
To this I may subjoin Rensselaerite, which frequently occurs in thick, heavy beds in connexion with the above.
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