Mr. Joseph Baldwin, formerly of Connecticut, now residing near Shawnee Town, in the Illinois Territory, has given us some interesting specimens of fluor spar. They are found not far from Shawnee Town, on the banks of the Ohio; and a few miles below where the Wabash joins the Ohio. The fluor forms the gangue of a lead vein, and we have pieces in which the lead and fluor are intimately blended. The lead ore is the common galena, or sulphuret, with a broad, foliated, or laminated fracture, and a high degree of metallic splendour. We reduced it to the metallic state, and it yielded a large product of very soft lead. On dissolving it in nitric acid, and applying the muriatic acid till precipitation ceased, the precipitate formed was _all redissolved_ by boiling water; nor, when submitted to cupellation did the lead leave any thing upon the cupel. We, therefore, conclude that it contained no appreciable quantity of silver. It is said to be very abundant at Shawnee Town. The fluor spar is very beautiful. Its colours, chiefly, very deep purple and violet; but still highly translucent; one specimen was entirely limpid. Both kinds, when thrown in coarse powder, on a red-hot shovel, in a dark place, phosphoresced, and the violet specimens in a very striking manner. Of the violet kind, we have a specimen nearly as large as a man's fist, which is perfectly pure and sound, and appears to have been a single crystal; the natural faces and angles were unfortunately obliterated by grinding on a common grindstone. We have others which are decidedly crystals of perfect regularity; cubes, and passages between the cube and octahedron. In some of the specimens, the disposition of colours, and the transmission of light is such as to show very clearly that the octahedron lies in the centre, as the nucleus or primitive form. The size and beauty of the specimens, and the abundance of this mineral near Shawnee Town, (provided there is no mistake in the case) clearly entitle this to be considered as the most interesting American locality of this beautiful mineral. Measures have been taken to investigate the subject more fully, and to obtain a supply of specimens. Quartz crystals appear to abound at the same place, besides various other minerals. ART. IV. _Carbonate of Magnesia, and very uncommon Amianthus, discovered near New-York.--Extract of a Letter from Mr. James Pierce to the Editor._ _New-York, May 18, 1818._ DEAR SIR,