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

minerals, such as occur in desert sands ; orthoclase, plagio-
clase, and muscovite mica being the most conspicuous.

These peculiarities might well lead us to doubt whether
the carbonaceous substance is truly coal, for it recalls the
structure of a vesicular lava flow and suggests that at one
time the material existed in the fluid state and might be an
inspissated product of a mineral oil.

Its specific gravity, however, determined by a diffusion
column from the purer parts, proved to be that of a household
coal; it gave off water and tarry matter when heated in
a closed tube, burnt with a white flame, and yielded very little
dissolved material when heated with chloroform, ether, and
other solvents. Whatever its origin, it does not now differ to
any marked degree from ordinary coal.

The second specimen is not laminated and is more highly
vesicular than the first, its substance, as seen in section, being
reduced to a network, enclosing comparatively large open
spaces which are not elongated in any direction. In the
network itself many minute vesicles are present, but mineral
fragments are rare.

The origin of this coal is obscure ; it may have been
formed by the growth of vegetable matter in quiet water, into
which mineral grains were at the same time carried by the
winds. Marsh gas evolved by the decaying vegetable matter
would account for the vesicles, and that in one of the
specimens these are flattened out in the planes of lamination
might be due to its having been formed nearer the bottom
than the top of the deposit and thus under the pressure of
overlying layers.

22. Lo-t'o-ch'uan, Pei-shan (01). From a rocky kopje,
one mile NW. of Lo-t'o-ch'uan. Granophyre.

A much-jointed reddish flinty rock with a dark brown
patina. It consists of quartz and orthoclase in micrographic
growths, including negative spherulites. Ferro-magnesian
elements are absent, but a fine dust of iron oxide is scattered
through the rock and confers upon it its red colour. Iron
oxide also occurs in long lines as though deposited along
cracks, and in some cases it helps to define the outlines of the
constituents of a radiate micrographic growth.

23. Lo-t'o-ch'uan (02). From a rocky kopje, eighteen
miles NW. of Lo-t'o-ch'uan. Biotite Granite.

White granite speckled with black mica.

It consists of large hypidiomorphic crystals of perthitic
orthoclase which sometimes include smaller crystals of
oligoclase or corroded fragments of muscovite. A little
microcline is also present. Quartz is present, sometimes in
mosaics ; it invades the orthoclase and shows a tendency to
micrographic growths. Biotite occurs as a fragmentary re-
sidue, sometimes passing into chlorite with associated epidote;
it is strongly pleochroic—X, pale yellowish brown; Y and Z,
deep brown to black—and includes crystals of apatite as well
as zircon, with pleochroic haloes. There is a little muscovite
in corroded crystals.

24. Lo-t'o-ch'uan (03). From a detritus hillock near
Lo-t'o-ch'uan. Fine-grained Grit.

A dark grey grit; sp. gr. 2·7.

This rock is remarkably fine grained and contains a great
deal of secondary calcite, which rendered its analysis under
the microscope remarkably difficult. This was removed with
hydrochloric acid. Quartz, in splinters and angular grains,
is abundantly present; there is some felspar with albite
twinning which extinguishes at 16°; and a good deal of
muscovite in small flakes and ragged contorted laminae.
Some opaque white granules, probably leucoxene, are
scattered here and there.

24 a. (04 and 05). Quartz.
25. Lo-t'o-ch'uan (01). Rocky kopje, six miles NW.
of Lo-t'o-ch'uan. Quartz Mica Schist.

A highly schistose fragment of a rock composed mainly
of quartz, plagioclase felspar, and biotite.

The quartz is very clear, without vapour cavities, or with
very few, shows marked undulose extinction, and forms with
the plagioclase a mosaic of various degrees of fineness. The
plagioclase is twinned on the albite plan and may thus be
distinguished from the quartz, which it otherwise closely
resembles. Its refractive index is so nearly that of quartz
that one cannot determine the difference.

The biotite is fresh and extremely uniform in all its
characters, clear, slightly brownish yellow in colour, with
marked pleochroism: X, colourless; Y and Z, brownish
yellow. It is remarkable for the abundant presence of
pleochroic haloes, some surrounding zircon, others a mineral
not identified. One of these haloes, well defined and circular,
surrounding the pyramidal end of a crystal of zircon gave
·0355 mm. as the value of the radius of the halo, after
deducting for the radius of the zircon.

Some small grains of magnetite are scattered through the
rock.

26. Lo-t'o-ch'uan (02). Rocky kopje, eighteen miles
NW. of Lo-t'o-ch'uan. Adamellite.

The chief constituents are large hypidiomorphic crystals of
orthoclase and plagioclase, both for the greater part extremely
sericitized. The plagioclase is closely twinned on the albitic
plan with a maximum extinction of 15°, but as its index of
refraction cannot be determined it is impossible to say
certainly whether it is albite or oligoclase. Quartz occurs in
coarse mosaics and is interstitial. Hornblende and biotite
are fairly abundant. The hornblende is green and pleochroic,
with X, faint straw yellow; Y, dark green, and Z also green.
The maximum extinction angle is 14°.

The biotite rarely retains a trace of its original brown
colour and is grey by alteration, with pleochroism: X, straw
yellow or colourless; Y and Z, dark green. It contains
a good deal of apatite, often in fairly large crystals, and some
zircons which are surrounded by a pleochroic halo.

There is a good deal of secondary epidote and chlorite.
Iron ores were not observed.

27. Lo-t'o-ch'uan (03). Detritus hillock near.
Limestone.
A fragment of fine-grained grey limestone, consisting of
6 U 2