On the remarkable problem presented by the crystalline development of Calaverite

Abstract

The validity of Haüy's great law of the rationality of intercepts — better known as the law of rational indices—or its equivalent, the law of homogeneity of arrangement of the ultimate particles in a crystalline structure, has as yet never been seriously called into question : nevertheless, in the crystals of the telluride of gold, calaverite, we find characters which are to all appearance at variance with this law. As far as the author is aware and can ascertain, no difficulty of a precisely similar kind has ever been encountered before. Certain substances do, indeed, display the so-called optical anomalies; but these are, as was first established by Mallard, in reality in strict accordance with the actual crystalline arrangement.