BUILDING STONE— GRANITE—LIMESTONE—GYPSUM. 91 
stone favorably situated for furnishing blocks suitable for purposes of construction. ‘The broad 
region between San Francisco mountain and the Sierra Madre, although far from granite, is 
supplied with sandstone, and the western end with magnesian limestone, in layers, which may 
be found thick enough for building purposes. The sandstones and marls of the gypsum forma- 
tion are not suitable for building, but the grey or yellow sandstone in the vicinity of Zuii will 
probably be found suitable for abutments and bridges. . Carboniferous limestone could probably 
be obtained in the Sierra Madre. The limestone found in such thick beds in Cañon Diablo 
would also become available for building, and we may conclude that it is not only an excellent 
material, but easily worked. 
From Fort Smith to Albuquerque, it is probable that the carboniferous limestone, especially 
at the extremes, would be the best and most accessible building-stone. The sandstone, if con- 
veniently located, would also be valuable. "The sandstone of the cretaceous and gypseous strata 
is probably too friable to be made use of over this part of the route, although there are doubtless 
many places where firm blocks can be quarried from the table-hills or borders of the Llano. 
The valley of the Rio Grande can be supplied with stone from the limestone or granite of the 
Sandia range, and it is probable that the sandstone along the ravines and valleys west of the 
Puerco is sufficiently firm and enduring for use. 
There is an abundance of building material along the western part of the route in the numer- 
ous granitic ranges, the only parts of the whole line that are not well supplied being the two 
great table-lands on the east and west of the Rio Grande. .These table-lands are, however, 
bordered on each side by outcrops of carboniferous strata, limestone and sandstone, which can be 
transported each way towards the centre of the plateaux if required. 
GYPSUM. 
This mineral occurs abundantly along a great part of the route. It is found in thin trans- 
parent plates, in large opaque masses, or with a fine grain and translucency like alabaster, and 
in red masses with a plumose structure. It forms, in many places, extensive sheets or thin 
seams in the rocks, and at others thick imbedded masses, constituting a very considerable por- 
tion of the strata. Specimens of the several varieties mentioned above are found in the collec- 
tion, and are registered in the catalogue from Nos. 70 to 82, inclusive. Descriptions will also 
be found of the most interesting masses in Chapter X ; and the principal deposites, with their 
association and mineral characters, have already been described in the preceding chapters. A 
few observations only upon the uses of the mineral in the arts will be added here. 
I have already presented observations at length upon gypsum, its uses, and its origin, in the 
report on the geology of the 32d parallel, and the following remarks are in part extracted from 
that report: 
The applications of gypsum in the arts, both in its raw state and prepared, or ground into 
plaster, are multiplied and various. The uses of alabaster are well known. Large quantities 
are worked into ornamental objects—vases, statuettes, &c.—in the establishments of France 
and other places in Europe. The fibrous variety, or satin spar, is sometimes used for making 
ornaments and beads, called Roman pearls. But by far the most important applications of 
gypsum in the arts are those of plaster of Paris. In this state it is used for moulds, casts, 
statues, as a cement, for plastering walls, and for ornaments on ceilings. The crude, unburnt 
gypsum, when powdered, is largely used in agriculture as a fertilizer. Enormous quantities of 
this substance are thus annually consumed in the United States. It is brought from the quarries 
of Nova Scotia, and finds its way, by rivers, canals, and railroads, to nearly all parts of the 
country. Itis even taken in quantities from the seaboard, by railway, far into the interior, to the 
broad fields of northern Virginia, situated on the New Red sandstone. Some idea of the extent 
to which this substance is used in agriculture may be obtained from a knowledge of the amount 
taken from the quarries of Nova Scotia and New Brunswick, and exported to the United States, 
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