362 ledoux: aurichalcite 



010 and a dome. Belar observed the following forms: (104), 

 (101), (201), (301), (401), (501), (601). 



In 1896 Prof. G. Cesaro 3 described fragmentary crystals 

 found at Flemalle in Belgium. He considers the mineral as 

 orthorhombic on account of its optical properties. The prin- 

 cipal tabular cleavage was by him taken as the front pinacoid 

 (100). The frequency of wedge-shaped tables is due to a pyram- 

 idal hemihedrism. In order to obtain simple symbols for the 

 domes Professor Cesaro started from a unit brachydome much 

 steeper than that of Belar and corresponding to 



c = 8.71263. 



In 1897 Prof. G. B. d'Achiardi 4 ascribed the wedgelike crys- 

 tals of aurichalcite to twinning of simpler 

 monoclinic individuals, the lateral faces 

 of the wedges being contact faces of the 

 twins. The following constants were 

 determined : 



a : b : c = x : 1 : 1.6574 

 13 = 84° 15'. 



In 1908 M. L. F. Navarro, 5 of Ma- 

 drid, measured with the microscope five 

 crystals of aurichalcite from Ondarroa, 

 F IG . i Vizcaya, Spain. The face-angles of the 



three-pinacoid measured on three crys- 

 tals gave the following measurements: 



(a) = 82° 34' ± 11' 



(b) = 80° 35' ± 21' 



(c) = 77° 55' ± 16' 



angles which may be regarded as a, (3, and y or their supple- 



3 Description des Mineraux phosphates, sulfates, et carbonates du Sol Beige. 

 Mem. de l'Acad. Roy. des Sciences, etc., de Belgique, Bruxelles, 53: 1-134. 1897. 



4 Aurichalcite de Campiglia Maritima et Valdaspar. Atti Soc. Tosc. di Sci. Nat. 

 Memori, 16: 1-15. 1897-98. 



6 Bol. R. Soc. Esp. Hist. Nat. Madrid, pp. 117-119. February, 1908. 



