MINERAL from GREENLAND. : 373 



3. A flat prifm, with the acute angle of 63 replaced by 

 one plane, and terminated by an acumination, having 

 three principal facettes fet on the larger lateral planes, with 

 which the centre one meafures 125° and 55 . Of this 

 fpecimen, an engraving is given in the annexed Plate, 

 Fig. 2. 

 Specific gravity, according to my experiments, 3.533. The 

 fpecimen appears to be nearly, though not abfolutely, pure. 

 This fubflance, however, is fo very much mixed with mica, 

 that no reliance can be placed on any of the trials which have 

 been made. Count Bournon, furprifed at the low fpecific gra- 

 vity noted by Mr Allan, which was 3.48o,broke down one of 

 the fpecimens which had been fent him, in order to procure 

 the fubflance in the pureft ftate pofflble, and the refult of four 

 experiments was as follows, 4.001 



3-797 



3-654- 



3-H9 

 In a fubfequent experiment of Mr Allan's, he found it 3.665. 



From thefe it appears, that the fubflance is not in a pure ftate. 



Its colour is fo entirely the fame with the mica, with which it 



is accompanied, that it is only by mechanical attrition that 



they can be feparated. 



Colour, brownifh-black. 



External luftre, dull 3 internal, ftiining and refinous, flight- 

 ly inclining to metallic. 



Fracture, fmall conchoidal. 



Fragments, indeterminate, fharp-edged. 



Opake. 



Semi-hard in a high degree. Does not fcratch quartz nor 

 felfpar, but fcratches hornblende and crown-glafs. 



Brittle. 



Easily 



