c. Chalcedony. This species is brought down the Mississippi or Missouri, and deposited in small fragments along the Missouri shore. It also constitutes the principal layers in the thin tabular, or mamillary masses, which constitute the basis of the radiated quartz. Most commonly, it is bluish-white, or milk-white.
d. Agatized Wood. Fragments of this mineral are brought down the Missouri, and deposited, in occasional pieces, along the banks of the Mississippi.
e. Hornstone—Chert. This substance appears to have been imbedded extensively in the calcareous strata of the Mississippi valley; for it is scattered, as an ingredient, in its diluvions. Frequently it is in chips, or fragments, all of which indicate a smooth conchoidal fracture. Sometimes it consists of parts of nodules. Sometimes it is still solidly imbedded in the rock, or consolidated strata, as on the coast below Cape Girardeau, Mo. Indeed, so far as observation goes, it characterizes all the district of country between the western banks of the Mississippi river, and the great prairies and sand deserts at the foot of the Rocky mountains. Its color is generally brown, with different shades of yellow, black, blue, or red. It appears nearly allied to flint, into which it is sometimes seen passing. It runs also into varieties of jasper, chalcedony, and common quartz; and the different gradations from well-characterized hornstone, until its distinctive characters are lost in other sub-species of quartz, may be distinctly marked. The barbs for Indian arrows, frequently found in this region, appear to have been chiefly made of hornstone.
f. Jasper. This mineral also appears to have been imbedded in the silico-calcareous rocks of the western valley; and it is found, in the fragmentary form, on the banks of the Mississippi, and also on its plains below the Rocky mountains. The fine yellow egg-shaped pebbles of White river, are common jasper. Several specimens, picked up in a desultory journey, possess striking beauty. The first is a uniform bottle-green, very hard, and susceptible of a high polish. The second is the fragment of a nodular mass, consisting of alternate concentric stripes of green, brown, and yellow; the colors passing by imperceptible shades into each other. A specimen found in Potosi consists of alternate stripes of rose and flesh red.
g. Agate. This mineral is picked up, in a fragmentary form, along the banks of the Mississippi. Its original repository appears to have been the volcanic and amygdaloidal rocks about its sources, which have been extensively broken down by geological mutations, during ante-historical periods. The fragments are often beautifully transparent, sometimes zoned or striped. Sometimes they are arranged in angles, presenting the fortification-agate. The colors are various shades of white and red, the latter being layers of carnelian. All the pieces found in this dispersed state are harder than the imbedded species, and are with difficulty cut by the lapidary.
h. Opal. A single specimen of this mineral, from the right banks of the Ohio, near Cave-in-Rock, Illinois, is of a delicate bluish-white, and opalesces on being held to the light. It is not acted on by acids. This locality is remarkable as yielding galena, heavy spar, blende, calcareous spar, fluor spar, pyrites, coal, and salt. It belongs to the great secondary limestone formation of the Ohio valley. It is cavernous, and yields some fossil impressions.
i. Red Ferruginous Quartz. This occurs as one of the imbedded materials of the diluvion of the Mississippi valley.
k. Rock Crystal. Very perfect and beautiful crystals of this mineral are procured near the Hot Springs of Arkansas. They consist, generally, of six-sided prisms, terminated by six-sided pyramids. Some of these are so perfectly limpid, that writing can be read, without the slightest obscurity, through the parallel faces of the crystals.
l. Pseudomorphous Chalcedony. Lake Pepin, Upper Mississippi. This appears to have been formed by deposition on cubical crystals, which have disappeared.
m. Tabular Quartz. West bank of the Mississippi, Missouri. Of a white color, semi-transparent. The plates are single, and the lines perfectly parallel.