462 



MINERALOGY 



the a pinacoid is often striated longitudinally. Terminations are 

 very rare. The two pinacoidal cleavages are at an angle of 106 

 with a cross parting parallel to the base. The hardness is remark- 

 able for its variation with the direction ; when tested parallel to 



FIG. 492. Cyanite, Pizzo Eorno, St. Gothard, Switzerland. 



the length of the crystal, on a, the hardness is nearly 7, but when 

 tested at right angles to this direction on the same ^f ace its hardness 

 is only 4. 



Cyanite is a mineral produced by metamorphic agents and is 

 never found as a pyrogenetic mineral in igneous rocks, but is asso- 

 ciated with staurolite and garnets in crystalline schists. 



Typical specimens are found at Litchfield and Newton, Con- 

 necticut ; in Yancey County, North Carolina. The rare white and 

 yellow variety rhaetizite is found in the Zillerthal and Pfitschthal 

 Tyrol. Most beautiful specimens occur at Pizzo Forno, St. Goth- 

 ard, Switzerland, in a paragonite schist, associated with staurolite, 

 with which it is often in parallel position. 



In its alterations cyanite is like sillimanite and andalusite. 





