C. Of Alluvial Depositions of Ores.
I agree with many mineralogists[1] in the opinion that these accumulations of ore have been originally true veins, worn down and removed by some cause or other from the place where they were formed; that they have been water-worn, and carried to a greater or less distance, where they have been covered by alluvial soil. These washed ores occur every where in similar situations, either in a plain, or in open and very low-lying vallies, in beds or strata, which are generally at a small depth below the surface of the ground, and often
- ↑ Klaproth's Mineralogical Observations on Cornwall, p, 11.
Mr. Jars believes these fragments to be remains of heaps of refuse from the ancient unskilful working of the mines, which by inundations have been washed down from the mountains, and formed beds in the vallies. Ibidem, p 11.
Pryce, who was a practical miner, divided the alluvial ores of tin into different kinds. “ The shade is disjunct, and scattered to some declined distance from its parent lode, and it is pebbly or smoothy angular of various sizes, from half an ounce to some pounds weight.” Stream tin ore is the same as abode, but smaller sized, or arenaceous. “ It is the smaller loose particles of the mineral, detached from the bryle or back of sundry lodes, which are situated on hilly ground, and carried down from thence by the retiring waters, being collected in large bodies or heaps in the vallies. In the solid rock of the valley there is no tin ore, but immediately upon it is deposited a layer of stream tin of various thickness; perhaps over that a layer of earth, clay, gravel, &c. upon that again another stratum of tin ore, and so on successively, stratum super stratum according to their gravity, and the different periods of their coming thither.” Pryce Mineralogia Cornubiensis.
