GUIDE TO THW MIXKKAIAM J I< ' i <> I .1.1 :< I I <>XS 



101 



columnar and granular masses. The luster is vitreous to dull, 

 and the color is usually gray, dull green or white, sometimes 

 bluish or reddish. 



Wernerite occurs in metamorphic rocks and is abundant in 

 granular limestone near the contact with granite <>r other igne- 

 ous rocks. It is associated with pyroxene, am- 

 phibole, apatite, etc. In New York wernerite 

 is found in Orange, Essex and Lewis counties 

 and abundantly in Jefferson and St Lawrence 

 counties. 



Vesuvianite (idocrase) 



Yesnvianite is a basic calcium-aluminium 

 silicate of uncertain formula with some of 



Fig. 219 



the calcium replaced by manganese and wernerite 

 some of the aluminium by iron. Fluorin and titanium may be 

 present. 



The crystals are tetragonal, prismatic or pyramidal in habit, 

 the prismatic crystals often exhibiting the general type shown in 

 fig. 220. Columnar masses occur straight, radiated or irregular, 

 often producing characteristic striations parallel to the vertical 

 axis. The luster is vitreous to resinous and the 

 color commonly brown, green or some interme- 

 din te shade, rarely yellow or blue. 



Vesuvianite commonly occurs as a contact min- 

 eral from the alteration of impure limestone; also 

 in serpentine, chlorite schist, gneiss and other 

 metamorphic rocks; in the former case it is usually 

 associated with garnet, phlogopite, pyroxene, wollastonite, etc. 

 It is found in Canada, .Maine. New Hampshire and Yew Jersey 

 and in Orange county and other localities in New York. 



Fisr. 220 

 Vesuvianite 



Zircon (hyacinth) ZrSiO, 



Zircon is ;i silicate of zirconium usually containing a little 

 iron sesquioxid. 



It occurs in tetragonal crystals, prismatic in habit, of the 

 genera] types shown in ti^ r . 221 -'■',. but sometimes pyramidal 



With the prism only slightly developed. Twins similar to those 



of cassiterite and rutile occur. Zircon is also found in irregular 

 lumps and grains. The luster is adamantine and the color 



