Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/37

Rh principally between the sixty-six and eighty-six fathom levels, in considerable quantity, often in well-defined crystals, and occasionally intermingled with native copper. Above it, the lode abounded with fluate of lime, frequently very solid, and so pure, that they, whose business it is to assay copper for the miner and the purchaser, preferred it as a flux to that of any other mine. Among this fluate of lime, and sometimes intimately mingled with it, considerable quantities of the yellow copper ore were found, and some arsenical pyrites containing 4 or 5 per cent. of copper, though comparatively little of that gossan, which, as will presently be noted, constituted the greater part of the Muttrell Lode; nor was the arseniate of copper discovered in any part of this lode, west of the junction of it with the Muttrell Lode.

The Muttrell Lode is one, to which no other lode hitherto discovered in the County of Cornwall bears any analogy. Throughout almost the whole length of its working, but particularly in that part, above, below, and in which was discovered the great deposit of red oxyd of copper, with the beautiful varieties of which this mine has enriched the cabinet of the mineralogist, this lode abounded in an ochreous substance, frequently accompanied by quartz, which from its appearance may be termed an argillaceous oxyd of iron; and which, sometimes for a considerable length and depth, constituted alone the great body of the lode. This substance is always considered by the miner as an indication of neighbouring riches; it is technically called gossan, and is denominated kindly, or very kindly, in proportion to the darkness of its hue, and the looseness of its texture. Through this gossan they sunk in the Muttrell Lode forty-six fathoms, and almost as many above the adit, before they arrived at any considerable quantity of the red oxyd of copper, which afterwards continued through a space ten fathoms in depth,