328 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



pegmatite vein abounding in albite and spodumene and closely resembling 

 the occurrence at the Manning farm, described above' (see p. 326). This 

 lies just across the north line of Northtield, near the house of M. A. Brown, 

 on the Winchester road. 



GARNET IN PEGMATITE WITH COMPLEX PARAMORPHIC BORDER OF ZOISITE- 

 HEMATITE, EPIDOTE-FIBROLITE, AND MUSCOVITE. 



In the coarse inuscovite-granite that occurs on the Gulf road in the 

 southern part of Northtield and cuts the Goshen mica-schist which farther 

 east becomes tibrolitic and is called the Brimfield schist, several interesting 

 garnets have been recently discovered by Mr. C. H. Webster. (PI. II, 

 fig. 4.) They are nearly an inch across, of deep-red color and of trapezo- 

 hedral form, with a narrow dark-red liand surrounding them which is in 

 places spotted with green. Outside this is an opaque white border, 3-7™™ 

 broad, which looks like saussurite. 



The garnet under the microscope is evenly cleaved and almost free 

 from inclusions. There are a few rounded blebs of the quartz-niuscovite 

 mixture or of the zoisite-hematite mixture which is found in the border. 



This border layer is largely composed of zoisite in stout grains, which 

 shows low polarization colors, high refraction, a divergence of optical axes 

 of 45°, and is optically positive. The hematite is deep-red to black, and 

 occupies regular and close cleavage fissures in the zoisite, often so regular 

 as to recall the cross-section of a tabulate coral. This layer is joined to 

 the garnet by a suture, which is very intricate, so that lobes of the two 

 minerals penetrate deepl\' into each other and rounded blebs of the zoisite 

 are cut oft' in the garnet. While thus intricately joined interiorly, the 

 zoisite mixture forms exteriorly quite smooth crystal faces for the garnet. 



Outside this first layer is a delicate and very thin layer of green 

 epidote, which folds into every irreg'ularity of the last layer and extends 

 continuously over all the surface of the latter and around all inclosed por- 

 tions of the same. It has rather moderate absorption and extinguishes in 

 proper i-elation to the cleavages for epidote. The outer layer is a mass of 

 niuscovite blades felted with a fine-fibrous mass of fibrolite needles arranged 

 in beautiful plumose and tufted groups in a general way radially to the 

 surface of the g-amet. 



