PROCEEDINGS 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



VoL.XI,No. I, pp. 1-16 Figs. 1-8 March 31, 1909 



SOME CALCITE CRYSTALS WITH NEW FORMS. 



By Waldemar T. Schaller. 



1. calcite from andreasberg 



Several specimens of calcite labeled " Andreasberg, Harz Mts.," 

 were purchased from a local mineral dealer. One specimen shows 

 large tabular crystals with only the base {0001} and prism |10iO|. 

 Other specimens consist of groupings of tabular crystals which are 

 somewhat unusual in their combinations. These tabular clacites 

 are arranged in superimposed parallel, or nearly parallel groupings 

 forming vertical columns several cm. long, the individual crystals 

 being up to 13 mm. wide and to 5 mm. high. The dominant forms 

 on these crystals are the base jOOOlj and prism {1010} but charac- 

 teristically all of them also show the new prism j { 7.6.13.0 1 as narrow 

 rounded faces. Very narrow faces of 5 { 0551 ] and minute faces of 

 2;{2131| are frequently present. Some of these crystals which 

 seemingly consist of a single crystal show an easy parting parallel to 

 the base and may be built up of numerous thinner tabular ones in 

 parallel position. Associated with these calcites are numerous four- 

 lings of harmotone. 



Measurements of the 9^ angle for 5{0551| varied from 78° 38' 

 to 78° 47'; calc. = 78° 32'. 



The dihexagonal prism faces are bright but rounded, so that no 

 accurate measurements could be made. They gave, however, a 

 bright signal in the mass of reflections caused by the rounded sur- 

 faces and the measurements given below were of this bright signal. 



