国立情報学研究所 - ディジタル・シルクロード・プロジェクト
『東洋文庫所蔵』貴重書デジタルアーカイブ

the rock. They consist of a glassy base in which, as seen
between crossed nicols, clearer alternate with darker bands.
The clearer bands are sometimes formed of a quartz mosaic,
and when they are very thin this mosaic may be reduced to
a line of single individuals : sometimes, however, the bands
consist of spherulitic growths having a positive sign.

The rock is not a consolidated volcanic ash, as a super-
ficial examination might suggest, but a rhyolite which was
broken up during flow, the resulting fragments being caught
up and carried along by that part of the stream which still
remained fluid.

17. Ming-shui, Pei-shan (014). From rocky knoll two
miles NW. of Ming-shui. Contorted Mica Schist.

A dark greenish-grey rock with silvery mica on the
foliation surface. Sp. gr. 2·78.

Muscovite mica is one of the most conspicuous constituents
of the rock, which repeats on a small scale the structure of
a much-folded mountain chain with folds, overfolds, and over-
thrusts in great variety: quartz mosaics follow the course of
the mica; their constituent grains are repeatedly broken
across in the direction of the once active pressure and show
strong undulatory extinction. Grains of felspar sericitized
too completely for exact determination contribute to the
structure, often occurring as 'eyes'. They extinguish
parallel to their cleavage, which is often well marked and
sometimes emphasized by lines of muscovite which has
developed along them and gives them a fallacious appearance
of albite twinning.

Garnets are fairly numerous; they are colourless, some-
times quite fresh and unbroken, but more usually fractured
along lines in the direction of pressure. Along these lines
chloritization has occurred, sometimes transforming nearly
the whole of the original substance. In some cases the
garnets are drawn out into lenticles; in others bent into
conformity with the cusp of a sharp fold. Streaks of crushed
magnetite are interspersed with the muscovite and conform
to its folds.

Tourmaline is represented by a few well-formed, bluish-
grey crystals, with pleochroism: O, bluish grey; E, almost
colourless or faint yellow.

Some stray fragments of biotite may be seen, with pleo-
chroism, X, faint yellow; Y and Z, deep greyish green.

18. Ming-shui, Pei-shan (015). NW. of Ming-shui.
Rocky ledge near Wadi, ten miles NW. of Ta-shi-kou.
Salmon-red Granite.

This consists of large crystals of orthoclase, microcline, and
oligoclase, mostly hypidiomorphic and remarkably fresh;
abundant quartz mosaic; a very little biotite,—pleochroism,
X, brown; Y and Z, black; a larger quantity of muscovite
which sometimes includes residual biotite, and finally and
most interesting, garnets, in much-fractured and corroded
crystals of a faint red colour.

Iron ores and apatite do not appear to be present.

19. Ming-shui, Pei-shan (016). From same locality
as (015). White Granite.

Orthoclase, with occasional perthitic structure, and oligo-
clase in large as well as small idiomorphic or hypidiomorphic
crystals form the greater part of the rock.

Quartz, with numerous gas pores, fills up the wide inter-
spaces between the felspars, sometimes in single individuals,
more often as a mosaic.

Biotite is present but not abundant; it sometimes contains
zircons with their accompanying haloes, and is generally rich
in apatite which forms comparatively large crystals. Most
of the biotite has been altered into chlorite and epidote.

Magnetite is well represented, especially in association with
the altered biotite.

The felspars, especially the orthoclase, are for the greater
part much sericitized, but some are remarkably fresh.

20. Pei-shan (018). Taken from a cliff twenty-three
miles NW. of Chin-êrh-ch'üan. Zoisite Hornblende Schist.

A fragment of a light green rock, with ill-developed
schistosity and traversed by quartz veins.

Under the microscope it presents a marked parallel
structure, strands of lighter and darker appearance running
in one direction, with which also the long axes of the con-
stituent minerals correspond.

The lighter streaks consist of an almost colourless amphibole
(actinolite) which extinguishes at 15° and is only faintly
pleochroic—X, colourless; Y and Z, faint green—together with
quartz, albite, and sphene. The darker streaks also consist
of these minerals, but to them is added another constituent
which is granular, and of high double refraction which
diminishes its transparency. This was found very difficult
to identify, and the rock slice was therefore submitted to
Dr. H. H. Thomas, Petrologist to the Geological Survey, who
was able to show that it possesses all the distinctive characters
of zoisite.

Some thin veins traverse the rock, cutting across the
parallel structure; some of these consist of calcite, some of
calcite and quartz, and others of an isotropic substance,
conjecturally regarded by Dr. Thomas as opal.

Dr. Thomas adds that the rock recalls some of the
'calcfintas' which occur around the granites of Devon and
Cornwall.

21. Mou-wu, Pei-shan (01), beyond Mao-mei.
Vesicular Coal.

The collection contains two small specimens of this
remarkable substance. One is a laminated fragment, com-
posed chiefly of dull lustreless layers which soil the fingers.
With these are intercalated bright lustrous layers, and the
whole resembles an impure coal.

Under the microscope this coal, which is opaque and
apparently structureless, is seen to be highly vesicular. The
vesicles in some of the laminae are comparatively small and
elongated for the most part in the plane of the laminae; in
others they are much larger and very irregular, extending
upwards across the laminae as well as with them. Further,
the substance of the layers is found to include, scattered
sparingly through it, a number of angular fragments of various