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

is very finely granular, and it owes its opacity to its structure,
its component granules being transparent.

65. Altmish-bulak, Kuruk-tāgh (02). *Grit.*
A fine-grained grey grit, breaking with irregular fracture;
composed chiefly of angular grains of quartz, but a good
deal of felspar, both orthoclase and plagioclase, is present,
much of it quite fresh. There are many opaque white grains

SOUTHERN EDGE OF TAKLAMAKĀN

66. Kara-tāsh (01). From terminal stony ridge on Sai,
three miles to W. of Tailik-tutkan, Endere-Charchan route.
*Fine-grained Grit.*
A remarkably fine-grained grit, composed chiefly of grains
of quartz ranging mostly from ·004 to ·02 mm. in diameter,
and so compact that, except for scattered dust of sericite, it
appears in ordinary light to be a homogeneous continuum.
A few sericitized crystals of orthoclase occur here and there,
and also of magnetite and pyrites. One or two veins of
quartz mosaic cross the slice, and there is a little secondary
calcite.

67. Kara-tāsh (02). Same locality as No. 66. *Grit.*
A coarser grit consisting chiefly of angular, and some
rounded, grains of quartz with an interstitial finer ground
mass. Some sericitized felspar and fresh oligoclase are
present, as well as secondary calcite, chlorite, and ferric
hydrate.

68. Imām-Jāfar-Sādik, S. of Taklamakān (01). Pebbles
from sacred hill of Imām-Jāfar-Sādik Ziarat (25. i. 1901).
*Spherulitic Rhyolite.*
This is a rock of very heterogeneous structure, but its
most striking character is its well-marked but much-disturbed
fluxional banding.
Between crossed nicols illuminated streaks with a thread-
like structure resembling that presented by the material of
spherulites are seen, but the threads, instead of being directed
radially, run in parallelism with the length of the streak;
sometimes minute elongated prisms of orthoclase may be
seen within a streak, also running parallel, swimming with
the stream. These and the threads themselves extinguish
parallel with their length and give a negative optical sign.
On encountering a phenocryst or patch of coarser material
they bend round it or enclose it as an 'eye'.
Bordering these streaks and sometimes composing them,
negative microspherulites occur, and in places, acting as
foreign bodies, large spherulites, which, however, are rarely
spherical and are sometimes drawn out into long fusiform
bodies in the direction of the flow.
In addition, bands and patches of a comparatively coarse
mosaic of quartz or intergrowths of quartz and felspar are
present and as well whole or fragmentary phenocrysts of
orthoclase, microcline, and oligoclase albite. From the
phenocrysts spherulitic growths sometimes proceed.
No biotite is present, but there are several patches of
epidote. Magnetite appears to be replaced by sporadic
crystals of pyrites.

and some iron ores. Secondary calcite exists, but is not
abundant. The ground mass is difficult to analyse: richly
scattered through it are minute particles which are often
rod-like, resembling bacteria in form and size; their refractive
index is above that of balsam, and they seem to extinguish
parallel to their length; but they are too minute for identi-
fication.

69. Imām-Jāfar-Sādik (02). *Rhyolite.*
This is a rather remarkable ck . It is constituted of
similar material to that of the preceding specimen, but
spherulitic growths are rare. The fluxion structure is clearly
shown by the interstitial glassy basis in which the crystalline
constituents are immersed; but what is most striking is the
fragmentary state of all these constituents. The quartz in
particular arrests attention; it has been broken up into
forms that recall those of the broken glass in volcanic ash,
apparently as a consequence of the presence of vesicles or
included globules of base in the original crystals. Sometimes
the several fragments of a shattered individual remain in
sufficient proximity to show that it has been broken in place.
It would appear that the lava, after ceasing to flow and
already on the point of solidifying, but still plastic, had again
been set in motion and then completed its consolidation.
The felspars present are of the same kinds as those present
in No. 68, but there is stronger evidence of the original
presence of biotite, which is now represented by shreds in the
last stage of alteration. The rock is fairly fresh, but a little
secondary calcite is present.

70. Imām-Jāfar-Sādik (03). *Rhyolite.*
A completely crystalline, banded rock, which much re-
sembles a granophyre. Spherulites of various degrees of
fineness or coarseness form the greater part of the rock;
quartz occurs as the final product of consolidation.

71. Mirān (05). *Quartz Hornblende Schist.*
This dark green schist is composed chiefly of a quartz
mosaic with foliae of green hornblende and associated brown
biotite.
The hornblende is strongly pleochroic: X, pale yellow to
almost colourless; Y, deep green; Z, bluish green. Its angle
of extinction is 23°.
The biotite is also strongly pleochroic: X, faint yellow;
Y and Z, deep brown. Both it and the hornblende are
devoid of pleochroic haloes.
The quartz mosaic includes grains of anorthite twinned on
the albite plan; they are glassy clear, and but for the twinning
might easily be overlooked.
Minute crystals of magnetite are scattered through the rock,
and are particularly abundant in the numerous 'eyes' formed
by the swelling out of the quartz foliae; in one instance the
greater part of an eye is formed by a comparatively large
lenticle of magnetite.
These eyes are frequently dusty with fine granules of an
undetermined mineral, and often contain a good deal of apatite.

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