208 GEOLOGY OF PART OF CUBA. 
evidence of having been originally so. They are extremely variable in structure and 
composition. Whilst some are compact, crystalline, and abound in metalloide diallage 
and hypersthene, others are fibrous and magnesian, readily decomposing in the atmos- 
phere. With the serpentines occur also the euphotides. One can rarely traverse the 
savanas, even for the space of a few hundred yards, without meeting with irregular 
masses of diabase, amidst the ordinary serpentines. At Sabana Viga, for instance, the 
prevailing rock is serpentine; one variety of which is soft, talcose, and easily worked in 
the mining operations. Another variety is much harder; of a dark green colour, accom- 
panied with crystals of diallage of various colours, but most commonly of a bronze me- 
tallic lustre. This quality is so abundant here that we not unfrequently apply to it the 
name of Sabana rock. A third species is so compact as to require blasting, when it is 
encountered in shafts and adits. Amongst these beds occur others of very hard trap 
rock, or of diabase; also of quartz and hornblende. Some talcose fibrous beds, with veins 
of asbestos, occasionally intervene, and accompany the pure serpentine. Bands of meta- 
morphic rocks often intrude. In fact, so variable is the geological composition of this 
district, that scarcely two cubical yards can be found, which precisely assimilate. An 
attempt to define these varieties, would extend this article to a wearisome length. Such 
multitudinous and ever changing characters present themselves, on all sides, that it would 
be a hopeless task to particularize them. In most of the mines where galleries, and 
shafts have been driven, this varying character was perceptible at every foot, and indeed, 
at every inch of progress. A museum might be filled with specimens from a single 
locality. 
WHITE LIMESTONE. 
It has already been remarked that the rock which attains the greatest elevation in the 
Gibara region is the compact modified limestone. Although it may be true that this 
elevation may be due to an upheaving force or thrusting up from below, yet it seems 
certain that this rock is contemporaneous with the surrounding savana series. This is 
clearly exemplified at certain points, a few miles remote from the anticlinal axis; at 
which points it is seen distinctly interstratified with, and consequently of the same age 
as, the magnesian rocks.* 
As we approach the Port of Gibara from the Bahemes, the aspect of the coast is bold 
and striking. Mountains of strange forms, and isolated bluffs with precipitous faces; 
and serrated ridges; elevated saddle-shaped masses, steep and bare of vegetation, and 
shining white in the sun’s rays, range along the coast, at the distance of a few miles in- 
land. When we approach nearer, and pass amidst them, to the undulating savanas in 
their rear, and note them stretching far away to the east and to the west, we perceive 
* [t can neither be the lithographic, cavernous “Calcaire de Guisnes” described by Humboldt near Matanzas and Trinidad, 
containing fossils of the age of the London clay; nor is it the “ White Limestone,” of Mr. D. la Beehe, in Jamaica, whose 
fossils are also of the same age as the “Calcaire Grossier.” This Calcaire de Guisnes is the same rock which appa- 
rently forms, to the eastward, the limestone of Hayti; to the south the white limestone of Jamaica; to the south-west the 
Calcaire de Caribe in the environs of Cumana; and to the west the arid cavernous limestone which occupies the peninsula 
of Yucatan, 
