162 PHYSIOGRAPHY. 



THOMSONITE. 

 KOUPHONE-SPAB.. 



Thomsonite. BROOKE. Ann. of PhiL Vol. XVI. p. 193. 

 THOMSON. Ibid. p. 408. PHILL. p. 39. 



Prismatic. P + oo =r 90 4(X, BROOKE. Crystals 

 elongated in the direction of the axis, having 

 the apices engaged. Massive : composition co- 

 lumnar, radiating from common centres. 



Cleavage, parallel to Pr -f oo, and Pr -f- GO, form- 

 ing a rectangular four-sided prism, very easily 

 obtained. Fracture uneven. Surface smooth. 



Lustre vitreous, much inclining to pearly. Colour 

 white. Transparent ... translucent. 



Brittle. Hardness = 5-0. Sp. Gr. = 2-37, BROOKE. 



According to THOMSON and BERZELIUS, it consists of 



It intumesces before the blowpipe, and becomes snow-white 

 and opake, but does not melt. It occurs with axotomous 

 Triphane-spar, in the trap-rocks of Kilpatrick, near Dum- 

 barton in Scotland. 



THULITE. 



SPAR. 



Thulite. BROOKE. Crystallography, p. 494. PHILL. p. 211 



Cleavage, parallel to the sides of a rhombic prism- 

 of 92 30' and 87 30V 



