Plate 7. — Tliin Sections of Material from Greenfield and Meriden "Ash Bed." 



Figure 1. — Red hematitic trap with secondary albite in perfect twinned crystals 

 lining the interior of steam holes. Two large half-filled cavities 

 and three smaller ones, wholly filled, appear. The large porphyritic 

 plagioclase to the right is mottled from decomposition. Greenfield 

 near Cheapside village, at the electric railroad cut. See page 70. 

 Magnified 20 times ; crossed nicols. 



Figure 2. — The interstitial aqueous deposit of plagioclase (probably albite), diop- 

 side, and segerine-augite. The plagioclase has a dusty altered center 

 caused by an early change to calcite and a limpid exterior of later 

 formation, which resembles the secondary plagioclase of figure 1. 

 The diopside is marked by strong boundaries and distant cleavage. 

 The segerine-augite is in dark patches. The darker bordering por- 

 tions are altered to serpentine with development of cleavage. At 

 the border, patches of the black sand appear. At the top is an 

 isolated spherulite. Greenfield quarry, 20 feet above base of bed. 

 See page 70. Magnified 35 times ; crossed nicols. 



Figure 3. — Scoriaceous sandstone. The dark parts are the rusty sandstone, red in 

 the interior of the bands, and blackened by heat exteriorly. They 

 show mud flow. The light parts are irregular, limpid, plagioclase 

 grains. The mud has shrunk away at the top from a first growth of 

 this kind, leaving a thin film of black grains, and in the narrow space 

 a more limpid, plagioclase growth occurs. In the center of the older 

 growth is a highly refringent mineral (datolite ?) showing a micropeg- 

 matitic structure with the plagioclase. See page 71. Greenfield, 

 Cheapside cut. Magnified 20 times. 



Figure 4. — Greenish brown glass with yellow borders, which are devitrified in 

 series of small spherulites with darker centers. The glass has been 

 shattered while the fragments were slightly plastic. The fragments 

 are in place in the slide and the cavities are partly filled by a sec- 

 ondary water-deposited albite growth. See page 74. From Meriden 

 "ash bed," near top on South path. Magnified 35 times. 



Figure 5. — Hyalopilitic diabase from the Meriden "ash bed." Base formed of 

 tufted, feathery, and fasciculate groups of beaded threads. Large 

 olivine at right, large augite full of glass enclosures on left. Contact 

 of basal bed on glass breccia. See page 72. Magnified 35 times. 



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