356 
APPENDIX. 
rectangular but spherical, and are not larger than the section of a pin. It is a clay-slate, and 
undoubtedly of sedimentary origin. 
No. 13. Quartzite.—Tomales bay. — It is difficult to give a description of this specimen. 
Although principally composed of quartz of a light gray color, it has an exceedingly regular 
structure like stratification, and this character is given to the mass by the presence of layers of 
delicate glassy crystals, the nature of which it is not possible to determine. They may he the 
faces of the grains of quartz, hut they appear to cleave like feldspar, and when the mass is held 
in certain positions they reflect the light in long lines. These reflecting lines are about one- 
sixteenth of an inch and parallel. The rock is probably metamorphic. It was presented tome, 
with No. 14, by Dr. A. Randall, of Punta de los Reyes. 
No. 14. Red Limestone.—Tomales bay. —This limestone has a dark, chocolate red color, and 
is irregularly veined with white and dark brown lines. It is compact and capable of taking a 
high polish, and may be considered as a beautiful ornamental marble. It occurs in considerable 
quantities, but whether largo blocks suitable for building can be quarried there had not been 
determined when the specimen was procured. Its position on the waters of Tomales bay renders 
it easy of access, and it can be readily transported to San Francisco. 
No. 15. White Limestone or Dolomite.—-Tomales bay. —This specimen is from the shores of 
Tomales bay, on the west side, where the rock occurs in considerable quantity, and is used for 
making caustic lime. It is white, coarse-grained ; the crystals large, and showing curved sur¬ 
faces when cleaved. Small, irregular patches and tufts of talc are found in the mass, and this, 
with the fact that the crystals have curved faces, leads me to consider the limestone as mag¬ 
nesian—a dolomite ; but this has not been determined by analysis. Small scales of graphite are 
also disseminated in the mass. It is probably a metamorphic limestone. 
No. 16. Porphyritic Granite.—Punta de los Reyes. —This specimen, which was taken from 
the quarry, does not show as much hornblende as is usually found in the rock of that locality, 
and the specimen consequently presents a lighter color than the mass of the rock. A distinct 
crystal of-feldspar, one inch in length, is seen in the mass, and this includes small crystalline 
masses of hornblende or magnetic iron, entirely isolated in the spar. A very dark colored mica, 
in indistinct scales, is found in the mass. 
No. 18. Granite — Macao , China. —This is a specimen of the rock which is so extensively used 
in San Francisco for buildings. It has a very pleasing pinkish-gray color, and a very even and 
desirable texture. Feldspar and quartz are the predominating minerals. Little or no horn¬ 
blende can be seen, but the gray color is produced by the isolated crystals of black mica which 
are very compact and small; so compact that the edges greatly resemble cleavage surfaces of 
hornblende. 
No. 22. White Granite — Williamson’s Pass. —This rock, at first sight, looks like a granular 
limestone or sandstone, but on examination the presence of a large amount of white glassy 
feldspar is proved by the reflection of light from the cleavage surfaces. Grains of white and 
translucent quartz are seen mingled with the spar, and very small fragmentary scales of a white, 
silvery mica. The rock is exceedingly compact and homogeneous. 
No. 23. Graphic Syenite — Williamson’s Pass. —This rock is a mixture of green hornblende 
and purplish feldspar ; the hornblende being disposed in irregular but angular crystals, the 
fractured or polished surface of the rock presents the appearance of Hebrew or Chinese charac¬ 
ters. 
No. 30. Talcose Slate—San Francisquito Pass. —This slate is light-green and consists chiefly 
