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『東洋文庫所蔵』貴重書デジタルアーカイブ

crystal ; a boundary between the two minerals is sharply
marked and is without reaction products. Hornblende
without included diopside is rare or absent. It presents the
forms (110), (010), and (100), is yellowish brown in colour,
with pleochroism : X, pale yellow; Y, light brown; Z, brown,
and extinguishes at 14°.

Secondary interstitial chlorite is present, but nothing has
been seen to suggest the original presence of olivine. There
is a good deal of magnetite.

56. Achchik-bulak, Kuruk-tāgh (01). *Adinole* (?).
A small fragment of a close-jointed rock weathering brown,
breaking along what appear to be planes of lamination with
a feathery fracture such as is often presented by clay iron-
stone, which the specimen much resembles. It fuses to a
black bead and colours the flame with sodium and potassium.
A qualitative analysis showed the presence of alumina, ferric
oxide, and lime.

The microscope reveals the presence of minute angular
fragments, crystals, and rounded grains of quartz, sections
which appear to be those of some felspar but often isotropic,
brownish granules, and associated rhombohedra of calcite or
siderite, and finally very minute granules, from ·001 mm.
to an average of ·002 mm., universally distributed through
the base, which behaves as an isotropic substance. To clear
the thin slice it was treated with dilute hydrochloric acid,
which removed all traces of calcite or siderite, but did not
affect the brownish or ochreous granules.

The slice was then treated with staining reagents which
coloured the very minute granules deeply, but did not affect
the base, which was more clearly displayed than in the
untreated slice and still preserved its isotropic character.

The specific gravity of the rock fragment was found to be
2·75.

57. Kuruk-tāgh (01 02). *Schistose Grit.*
Irregular fragments of grit, including minute pebbles of
quartz.

58. Arpishme (02). *Gypsum.*
Thin cleavage flakes of gypsum.

59. Iltar-ghush-bulak (01). *Gypsum.*
A fragment of what must have been a very large crystal.

60. P'o-ch'êng-tzŭ, Kuruk-tāgh. *Gritty Limestone.*
A fragment of red limestone, very similar in appearance to
some of the English Triassic grits.

It consists chiefly of small rhombohedra of calcite, on aver-
age ·0186 mm. in diameter, and severally bordered by ferric
hydrate, which is also dispersed in minute transparent scarlet
granules throughout the rock. There are also scattered
fragments of quartz, both angular and rounded, altered
felspar, and opaque altered ilmenite.

The rock dissolves readily in dilute hydrochloric acid, and
the solution yields on analysis alumina, iron, manganese,
lime, and a trace of magnesia. The residue consists of ferric
hydrate, orthoclase, quartz, cryptocrystalline grains, and a little
muscovite, as well as crystals of tourmaline, zircon, and rutile.

A vein of comparatively coarse mosaic calcite traverses the

slice, and accompanying this is a fibrous colourless mineral
of about the same refractive index as balsam, of low, double
refraction, and optically negative. It much resembles the
spherulitic material of a rhyolite; but the quantity at our
disposal is too small for its identification.

61. Bakri-changche-bulak, Kuruk-tāgh (01–04).
*Granophyre.*
These specimens are so similar that they might have come
from different parts of the same rock, and a single description
will suffice for all.

There is a small quantity of ground mass consisting of
minute crystals of quartz and felspar, but the greater part of
the rock consists of intergrowths of quartz and felspar as well
as abundant spherulites of the typical positive kind. Some
of the spherulites contain small elongated crystals of felspar
which lie athwart the radial structure.

Phenocrysts of orthoclase and a plagioclase which behaves
as albite, some of comparatively large size, are numerous,
and biotite, green by alteration, is scattered throughout the
mass in ragged flakes and linear strips which resemble agerine.
Pleochroic aureoles are present, surrounding in some
cases zircon, in others a small grain of iron ore. The
maximum diameter of the radii of the aureoles is ·0185 mm.

The felspars are much sericitized, and patches of secondary
muscovite are present in all the specimens, in some secondary
calcite also.

62. Bakri-changche-bulak (06 and 08). *Adamellite.*
These two specimens are also closely similar, as is 07,
which has not been cut.

They are a coarsely crystallized rock composed chiefly of
large hypidiomorphic crystals of albite and orthoclase with a
little microcline and perthite. The quartz mosaics are mostly
interstitial and dentate the margins of the felspar crystals.
Occasionally a pegmatitic growth is to be seen.

Biotite is present in small quantity only. The rock has
been subjected to considerable pressure, which has fractured,
dislocated, and even crushed some of its constituents. The
quartz shows undulatory extinction, and in specimen 08
a large albite crystal is crossed, at about right angles to the
lamination, by six more or less parallel cracks, along
all of which it has been faulted, and along some completely
brecciated.

63. Yardang-bulak. *Quartz.*
Two much water-worn crystals of milk-white quartz.

64. Āltmish-bulak, Kuruk-tāgh (01). *Calcareous Grits.*
A fine-grained, laminated grey grit, composed chiefly of
angular fragments of quartz, orthoclase, and plagioclase, with
subordinate vesicular volcanic glass, biotite, muscovite, and
chlorite. A few grains of calcite appear to be primary, but
the greater part of this mineral, which is abundant, is a
secondary product deposited in the interstices between the
constituent grains and sometimes replacing them.

Another interstitial substance, white by reflected and black
by transmitted light, is also present ; it lines the vesicles of
the volcanic glass and also occurs in well-defined grains. It