important and valuable being the famous Tabriz marble. This curious
substance appears to be a petrifaction formed by natural springs, which
deposit carbonate of lime in large quantities. It is found only in one
place, on the flanks of the hills, not far from the Urumiyeh lake. The
slabs are used for tombstones, for the skirting of rooms, and for the
pavements of baths and palaces; when cut thin they often take the place
of glass in windows, being semi-transparent. The marble is commonly of
a pale yellow color, but occasionally it is streaked with red, green, or
copper-colored veins.

In metals the country is thought to be rich, but no satisfactory
examination of it has been as yet made. Iron, copper, and native steel
are derived from mines actually at work; while Europeans have observed
indications of lead, arsenic, and antimony in Azerbijan, in Kurdistan,
and in the rocky ridges which intersect the desert. Tradition speaks
of a time when gold and silver were procured from mountains near
Takht-i-Suleman, and it is not unlikely that they may exist both there
and in the Zagros range. Quartz, the well-known matrix of the precious
metal, abounds in Kurdistan.

Of all the mineral products, none is more abundant than salt. On the
side of the desert, and again near Tabriz at the mouth of the Aji Su,
are vast plains which glisten with the substance, and yield it readily
to all who care to gather it up. Saline springs and streams are also
numerous, from which salt can be obtained by evaporation. But, besides
these sources of supply, rock salt is found in places, and this is
largely quarried, and is preferred by the natives.

Other important products of the earth are saltpetre, which is found
in the Elburz, and in Azerbijan; sulphur, which abounds in the same