260 



Summary of the Properties of the Large Porphyritic 

 Crystals of Anorthoclase. 



Colour — Flesh pink, subtranslucent to opaque. 



Crystalline form — Not determined. 



Cleavage — Perfect parallel to (001) and (010), the cleavage 

 angle being 90° 7'. 



Polysynthetic twinning after albite and pericline laws on a 

 very fine scale. Twinning after Carlsbad law frequent. 



Specific gravity — 2*582. 



Refractive index between lolS and 1-525. 



Dispersion — p > v. 



Composition — Oro3 Abg An 4. 



