This section is from the book "A Library Of Wonders And Curiosities Found In Nature And Art, Science And Literature", by I. Platt. Also available from Amazon: A library of wonders and curiosities.
The Labrador Stone, is a curious species of Feld-spar, or Rhombic Quartz, which exhibits all the colours of a peacock's tail. It was discovered some years ago by the Moravians, who have a colony among the Esquimaux, in Labrador. It is found of a light or deep gray colour, but for the most part of a blackish gray. When held in the light in various positions, it discovers a diversity of colours, such as the blue of lapis lazuli, grass-green, apple-green, pea-green, and sometimes, but more seldom, a citron yellow. Sometimes it has a colour between that of red copper and tornbuck-gray; at other times the colours are between gray and violet. For the most part, these colours are in spots, but sometimes in stripes on the same piece. The stones are found in pretty large angular pieces, appear foliated when broken, and the fragments are of a arhomboidal figure.