EXPLANATION OF PLATE 6. 
Figure 1.—From a photograph; illustrates structure of the “ com¬ 
pound ” spherulites of Silver Cliff (p. 425), § natural size, from section of a 
spherulite 3 feet in diameter. The white branching arms represent the 
earliest spherulitic development; they consist mainly of a dense bundle 
of feldspar fibers lying in a base of amorphous hydrated silica. The darker, 
mottled part between these arms consists of feldspar and quartz, the for¬ 
mer in fibers more or less regularly oriented with reference to the earlier 
crystallization. 
The outer zone consists of a dense microspherulitic band and of added 
spherulites of pronounced zonal structure, some of them being very distinct 
lithophysse. 
Figure 2.—From a photograph, f natural size ; illustrates features of a 
compound spherulite from Silver Cliff, described in detail on page 434. 
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