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Updated: June 8, 2025
The clay which separates these amygdaloid concretions arises from the decomposition of their crust. They acquire by the contact of the air a very thin coating of yellow ochre. South-west of the village of Parapara rises the little Cerro de Flores, which is discerned from afar in the steppes.
They found certain rocks, for the most part without stratification, and of a peculiar mineral composition, to which they gave different names, such as basalt, greenstone, porphyry, trap tuff, and amygdaloid.
The banks of these watercourses on the plains, as I have elsewhere observed, are the highest parts of the ground. This higher ground appeared here to rise towards the west, along the banks of the brook which, flowing also westward, seemed to run up hill. The soil was mixed with pebbles of vesicular trap, probably amygdaloid with the kernels decomposed, and containing particles of olivine.
Pretty soon she is at her usual relaxation, looking for shells, ivy berries and roots of wild vines to adorn that never-attainable home. The kindly, generous twilight, so unlike the swift shrift of the Florida levels, still lingers; and presently, amid bits of syenite, volcanic tuff and scoria, she has found this nodule of amygdaloid.
This red under-lyer is, in fact, a great deposit of red sandstone, breccia, and conglomerate with associated porphyry, basalt, and amygdaloid. According to Sir R. Murchison, the Permian rocks are composed, in Russia, of white limestone, with gypsum and white salt; and of red and green grits, occasionally with copper ore; also magnesian limestones, marl-stones, and conglomerates.
But untold ages ere this the waters of Leila were already frequented by men of another kind, by the flint-artists. Among the relics of their occupation I picked up, here, an unusually fine implement of the "amygdaloid" shape. Not a soul in Gafsa, native or foreign, could tell me who was the lady Leila that gave her name to this fountain.
I no longer travel upon horizontal paths, but over hills and steep ridges, across deep valleys and ravines. The hoof of my horse no longer sinks in light sand or dark alluvion. It rings upon rocks of amygdaloid and porphyry. The soil is changed; the scenery has undergone a change, and even the atmosphere that surrounds me. The last is perceptibly cooler, but not yet cold.
They consist in great part of diallage rocks and serpentine, and of an amygdaloid with calcareous kernels, and a base of serpentine.
I have never seen any other amygdaloid with the cells half filled in the manner here described; and it is difficult to imagine the causes which determined the earthy mineral to sink from its gravity to the bottom of the cells, and the crystalline mineral to adhere in a coating of equal thickness round the sides of the cells.
Before going to see the pyramids, we visited the caves in the hill-side not far from them, whence the stone was brought to build them. It is tetzontli, the porous amygdaloid which abounds among the porphyritic hills, a beautiful building-stone, easily worked, and durable. There was a large space that seemed to have been quarried out bodily, and into this opened numerous caves.
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