DOI Page / Citation link:
https://doi.org/10.11588/diglit.33567#0280
i6z}.
bution, and himself even became acquainted with them, for example, from Upper Egypt. This
latter circumstance evidently caused him to deviate again from his original proposition, and to give to
this hornblende-carrying granite the name of syenite, which already was employed by Pliny (xxxvi. 13)/
Werner, therefore, understood by syenite mixtures of felspar and hornblende both with without
quartz. As, however, in the further development of petrography, a sharper division between the acidic
and basic rocks proved to be desirable, the German geologists designated the quartzose varieties of
Werner's " syenite" as syenitic-granite or amphibole-granite, and used the name syenite exclusively for
the mixture of orthoclase and hornblende free from quartz. This to-day is, in Germany, the usual
terminology. Roziere followed a different course. He believed that the name of syenite must be given
to that rock which is found near the cataracts of the old Syene (Assouan), and in which the old
Egyptians had located their great quarries. But this stone, as was mentioned above, contains quartz.
For its corresponding modification which was free from quartz, Roziere proposed the name
because in the meantime it had transpired that, along with others, this variety occurs on Mount
Sinai. The French, English, and North American geologists for a long time followed at least the first
suggestion of Roziere, and have generally called the " amphibole-granite " of the Germans syenite ; on
the other hand, the second proposition of Roziere has nowhere received any continuous acceptance'; the
felspar, hornblende mixtures free from quartz have been called sometimes diorites and sometimes
greenstones, by the French, English, and North American petrographers, without particular regard to
the monoclinic or triclinic character of their felspar.^ Thus a very unfortunate confusion arose, which
until recently, has shown no signs of abatement, and now, it must be said, by a tendency in favor of the
German terminology. I follow here this latter, and need fear no misunderstanding if I again mention
that in Upper Egypt amphibole-granite is the predominating rock, but that both biotite-granite and
syenite are found there. The amphibole-granite was employed with especial preference by the
Egyptians for ornamental and architectural purposes; according to Delesse, the inside and outside
linings 4 of the great pyramids of Cheops consist of it, as well as the numerous sphinxes and sar-
cophagi, Pompey's Pillar, the sacred monolith of Sais, and the obelisks.
We have an extremely careful description of this Egyptian amphibole-granite (syenite of Roziere)
from the distinguished French geologist, A. Delesse.
As the New York obelisk is cut from this rock, I consider it desirable to give the more important
observations of Delesse concerning it.
According to him, the rock consists of quartz, orthoclase, oligoclase, mica, and often also of horn-
blende.^
The quartz is translucent and gray; it has occasionally a somewhat violet or smoky gray tint, which, as in
the case of the quartz of protogine, is derived from a small quantity of organic matter. The orthoclase has a
beautiful bright red, red, or yellowish-red color, which reminds one of the coloration of the orthoclase in the
syenite of the Vosges, but is much brighter; it forms crystals of several centimetres in length,—twins, as in the
case of granite rocks; it generally is the most prominent constituent of the mixture, is very often the mineral
most largely represented, and generally gives the rock its reddish color. (See Plate xliv, Fig. 4.)
Delesse found the specific gravity to be 2.568.
At a red heat it loses only 0.35 p. c. This loss is very little, as is generally the case with orthoclase. When
the felspar decomposes, it sometimes assumes a brown color, which is due to a little manganese oxide contained
in it and which is set free. The triclinic felspar has not a greasy lustre as in the syenite of the Vosges, and
* Kohler, yh%r73%/ 1788, ii, 824.
" As little has the name hyposyenite, proposed by Dana for a mixture of orthoclase and hornblende free from quartz,
been able to graft itself on the terminology.
"D. Forbes, "The Study of Chemical Geology," London, 1868, 10.
' In Delesse's original Memoire," cited elsewhere, only the inside of the pyramid is mentioned.—P. F.
° Delesse on the light red syenite from Egypt, in Karsten's and Deehen's /hr JAA/Azg*, <37^
Berlin, 1851, xxiv, 63, 70.
bution, and himself even became acquainted with them, for example, from Upper Egypt. This
latter circumstance evidently caused him to deviate again from his original proposition, and to give to
this hornblende-carrying granite the name of syenite, which already was employed by Pliny (xxxvi. 13)/
Werner, therefore, understood by syenite mixtures of felspar and hornblende both with without
quartz. As, however, in the further development of petrography, a sharper division between the acidic
and basic rocks proved to be desirable, the German geologists designated the quartzose varieties of
Werner's " syenite" as syenitic-granite or amphibole-granite, and used the name syenite exclusively for
the mixture of orthoclase and hornblende free from quartz. This to-day is, in Germany, the usual
terminology. Roziere followed a different course. He believed that the name of syenite must be given
to that rock which is found near the cataracts of the old Syene (Assouan), and in which the old
Egyptians had located their great quarries. But this stone, as was mentioned above, contains quartz.
For its corresponding modification which was free from quartz, Roziere proposed the name
because in the meantime it had transpired that, along with others, this variety occurs on Mount
Sinai. The French, English, and North American geologists for a long time followed at least the first
suggestion of Roziere, and have generally called the " amphibole-granite " of the Germans syenite ; on
the other hand, the second proposition of Roziere has nowhere received any continuous acceptance'; the
felspar, hornblende mixtures free from quartz have been called sometimes diorites and sometimes
greenstones, by the French, English, and North American petrographers, without particular regard to
the monoclinic or triclinic character of their felspar.^ Thus a very unfortunate confusion arose, which
until recently, has shown no signs of abatement, and now, it must be said, by a tendency in favor of the
German terminology. I follow here this latter, and need fear no misunderstanding if I again mention
that in Upper Egypt amphibole-granite is the predominating rock, but that both biotite-granite and
syenite are found there. The amphibole-granite was employed with especial preference by the
Egyptians for ornamental and architectural purposes; according to Delesse, the inside and outside
linings 4 of the great pyramids of Cheops consist of it, as well as the numerous sphinxes and sar-
cophagi, Pompey's Pillar, the sacred monolith of Sais, and the obelisks.
We have an extremely careful description of this Egyptian amphibole-granite (syenite of Roziere)
from the distinguished French geologist, A. Delesse.
As the New York obelisk is cut from this rock, I consider it desirable to give the more important
observations of Delesse concerning it.
According to him, the rock consists of quartz, orthoclase, oligoclase, mica, and often also of horn-
blende.^
The quartz is translucent and gray; it has occasionally a somewhat violet or smoky gray tint, which, as in
the case of the quartz of protogine, is derived from a small quantity of organic matter. The orthoclase has a
beautiful bright red, red, or yellowish-red color, which reminds one of the coloration of the orthoclase in the
syenite of the Vosges, but is much brighter; it forms crystals of several centimetres in length,—twins, as in the
case of granite rocks; it generally is the most prominent constituent of the mixture, is very often the mineral
most largely represented, and generally gives the rock its reddish color. (See Plate xliv, Fig. 4.)
Delesse found the specific gravity to be 2.568.
At a red heat it loses only 0.35 p. c. This loss is very little, as is generally the case with orthoclase. When
the felspar decomposes, it sometimes assumes a brown color, which is due to a little manganese oxide contained
in it and which is set free. The triclinic felspar has not a greasy lustre as in the syenite of the Vosges, and
* Kohler, yh%r73%/ 1788, ii, 824.
" As little has the name hyposyenite, proposed by Dana for a mixture of orthoclase and hornblende free from quartz,
been able to graft itself on the terminology.
"D. Forbes, "The Study of Chemical Geology," London, 1868, 10.
' In Delesse's original Memoire," cited elsewhere, only the inside of the pyramid is mentioned.—P. F.
° Delesse on the light red syenite from Egypt, in Karsten's and Deehen's /hr JAA/Azg*, <37^
Berlin, 1851, xxiv, 63, 70.