Spodumene and its Alterations. 351 



Jar Albite, Tourmaline, and Spodumene : then Cleavelandite, 

 Quartz, Manganese-Garnet, and Zircon: and finally smoky Quartz, 

 with green and blue Tourmaline. The larger crystals of most 

 of these minerals penetrate through all the layers, and their 

 growth seems to have been continuous. 



At Clark's Ledge, in Chesterfield, the main granite-vein is of 

 the same general constitution as that just described, rarely show- 

 ing a few large Beryls. In the secondary vein no Spodumene 

 occurs, but the succession is in the same order. First, on either 

 wall, a saccharoidal albitic granite, with little Quartz and Mica, 

 and a few scattered imperfect black Tourmalines and Garnets : 

 then coarse Cleavelandite, with blue, green, red, and rarely 

 brown Tourmaline, and small quantities of the rarer minerals, 

 Microlite, Columbite, Cassiterite, Zircon, Cookeite, and Lepido- 

 lite ; all these, especially the Tourmaline, increase in quantity 

 and development toward the centre of the vein, which is filled 

 up by an irregular sheet of smoky Quartz. 



At Chesterfield Hollow, the granite of the main vein is of the 

 usual character, but shows no Beryl and little Mica. The suc- 

 cessive deposition of minerals in the secondary vein is first 

 Orthoclase, in huge crystals, large plates of Muscovite, some- 

 times 6 to 10 inches in diameter, and grayish-white Quartz. 

 Within this comes an irregular mass of a coarse albitic granite, 

 with green Muscovite, Spodumene, greenish-white Beryl, in 

 masses sometimes ten to twenty-five pounds in weight, coarse 

 Garnets, Columbite, in rudely-crystallized grains, up to half a 

 pound in weight, and a Zircon rich in uranium, in minute 

 double pyramids, rarely three-sixteenths of an inch in diameter. 

 Usually this albitic granite passes gradually into a mixture of 

 Quartz and Cleavelandite, in bunches of snow-white plates, en- 

 closing less Muscovite, — Manganese-Garnets in large and abund- 

 ant but imperfectly crystallized grains, — Zircon, — Spodumene, — 

 and yellowish- white Beryl in irregular masses. 



Finally, the core of the vein consists of an irregular sheet of 

 smoky Quartz, penetrated by long prisms of Spodumene, — green, 

 Beryl in small and good crystals, — Muscovite, in hexagonal 

 plates, often well crystallized, and up to two or three inches 

 across, as well as in sheets, scattered scales, and wavy films, which 

 in part seem to be altered to Margarodite, — Columbite and Zircon 



