Letter, from Antoni van Leeuwenhoek to the Royal Society, dated at Delft Signed autograph Observations of red sandstone taken from the cathedral at Utrecht after it had partly collapsed; comparing these sand grains to diamond; theory about the origins of diamond; observations of marble from Italy, Bentheim stone (from western part of Germany), alabaster, gold and silver ore from Sumatra Read to the Royal Society on 1 March 1704 9 red-chalk figures English translation is EL/L3/61 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 14, p 293 English translation printed in 'Philosophical Transactions', vol 24, no 289, p 1544 1 February 1704