Chapter Devil's Den to Diamond Jousts of D by Brewer's Phrase & Fable

most brilliant lustre. We say also, "A man of the first water."
   A rough diamond. An uncultivated genius; a person of excellent parts, but without society manners.

"As for Warrington, that rough diamond had not had the polish of a dancing-master, and he did not know how to waltz." -Thackeray.

   Diamond cut diamond. Cunning out-witting cunning; a hard bargain over-reached. A diamond is so hard that it can only be ground by diamond dust, or by rubbing one against another.

Diamond (Newton's favourite little dog). One winter's morning, while attending early service in Trinity College, Newton inadvertently left Diamond shut up in his room. On returning from chapel he found that the little fellow had upset a candle on his desk, by which several papers containing minutes of many years' experiments, were destroyed. On perceiving this irreparable loss, he exclaimed, "Oh, Diamond, Diamond, thou little knowest the mischief thou hast done!" (Diffusion of Useful Knowledge: Life of Newton, p. 25, col. 2.)
    Huygens, 1694, referring to this accident says: "Newtonum incidisse in phrenitin abhinc anno ac sex mensibus. An ex nimia studii assiduitate, an dolore infortunii, quod in incendio laboratorium chemicum et scripta quædam amiserat."

Diamond Hammer (A). A hammer or pick for "whetting" millstones. The diamond hammer is provided with several sharp-pointed teeth to give a uniform roughness to the surface of the stone. Also to a steel pick with diamond-shaped point at each extremity, to recut grooves in stone.

Diamond Jousts (The). Jousts instituted by King Arthur, "who by that name had named them, since a diamond was the prize." Ere he was king, he came by accident to a glen in Lyonnesse, where two brothers had met in combat. Each was slain; but one had worn a crown of diamonds, which Arthur picked up, and when he became king offered the nine diamonds as the prize of nine several jousts, "one every year, a joust for one." Lancelot had won eight, and intended to present them all to the queen "when all were won." When the knight laid them before the queen, Guinevere, in a fit of jealousy, flung them out of the palace window into the river which ran below. (Idylls of the King; Elaine).