Baie ter al Sl 
BE ae ea ee 
J. 8. Diller—Fulgurite from Mt. Thielson, Oregon. 255 
hydrate or sodium carbonate. The accompanying figure (fig. 1) © 
represents a section of one side of a lightning-tube and shows 
the relation of the fulgurite to the unaltered basaltic rock 
which appears beneath. Its line of contact with the fulgurite 
is irregular. The black-bordered olivine grains and crystals o 
feldspar project into it and show no prominent effects of the fu- 
sion, while the hypersthene is distinctly rounded on the edges 
and the groundmass has been melted much more readily than 
any other portion of the rock. The fulgurite is divided into two 
more or less distinct bands. The band (c) nearest the middle of 
the lightning-tube is a uniformly light coffee-brown glass, which 
-- — He 
REE Us 
Section of one side of a Lightning-tube from 
Mt. Thielson, Oregon. a, unaltered hyper- 
Sthene basalt; b, mixed zone; c, fulgurite. : 
contains a number of nearly spherical vesicles. Between the 
zone of pure fulgurite (c) and the unaltered rock (a) there is a 
narrower belt (6) in which the fusion has been less complete 
and the dark fluidal banding parallel to the length of the tube 
Is prominent. This zone is frequently more or less granular. 
It is not only penetrated by crystals of feldspar, hypersthene 
and olivine projecting from the adjacent rock, but envelops 
numerous crystal remnants of these minerals scattered through- 
out. It contains some small round bubbles, but they do not 
appear nearly so abundant as in the fulgurite described by 
Wichmann from Little Ararat; nor have I been able to dis- 
cover any radial arrangement in the longer axes of the larger 
vesicles. The superficial coating of fulgurite is composed wholly 
of coffee-brown glass without any marked fluidal structure. 
A striking feature of the fulgurite is the absence of all pro- 
ducts of crystallization from the electricfusion. It is true that 
fulgurite frequently envelops crystals and crystal fragments, 
