Frederick William Rudler

“ This optical effect, known sometimes as “labradorescence,” seems due in some cases to the presence of minute laminae of certain minerals, like göthite or haematite, arranged parallel to the surface which reflects the colour; but in other cases it may be caused not so much by inclusions as by a delicate lamellar structure in the felspar. An aventurine effect is produced by the presence of microscopic enclosures. The original labradorite was found in the neighbourhood of Nain, notably in a lagoon about 50 m. ”