Cervandonite [SEP] named after
it has proven to be problem due to the extreme scarcity of single crystals and its unusual replacement of silicon and arsenic. Cervandonite is named after the location where it was first described, Pizzo Cervandone (Scherbadung), Italy in the Central Alps.
Structure.
The current work is based on a single- crystal fragment of cervandonite measuring 0.08 X 0.03 X 0.02 mm. The exact fragment was re-examined with MoKα radiation using BRUKER Apex II diffractometer equipped with a 2K CCD detector. Through the use of X
Due to the unusual diadochy, the variable composition of cervandonite might consist of an assembly of more or less twinned microdomains. Since cervandonite contains different values of As/Si and unit- cell parameters, has observed one type of superstructure.
Physical properties.
Cervandonite- (Ce) has a monoclinic cell with Z=6. The monoclinic structure was refined as a trigonal subcell using 411 reflections with I  2σ (I), R1=0.320, wR2=0.0887. The R- centered cell can be transformed with, a 6.508 (1), c