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238 Notice of Messrs. Foster and Whitnei/s Report^ SfC. 



"The Cliff mine is situated on Keweenaw Point, about three 

 miles from the lake shore, in the southwest quarter section 36, 

 township 58 north, range 32 west. A range of elevated hills 

 sweeps round in a crescent form, trending in a southwesterly di- 

 rection, and forming the western boundary of the valley of Eagle 

 river. In places these hills attain an elevation of 800 feet, and 

 towards the valley present bold mural escarpments, while on the 

 side exposed to the lake the slope is gradual. This range is 

 composed of trappean rocks. The summit is capped by a hard 

 crystalline greenstone, as at the Cliff mine, passing into a feld- 

 spathic porphyry, as at the Albion. Below, and forming the 

 base of the ridge, is a belt of granular trap, occasionally amyg- 

 daloidal. Between the two, there is a thin belt of slaty chlorite 

 about twelve feet in thickness. These belts dip to the north at 

 an angle of 45°, conforming in this respect to the inclination of 

 the detrital rocks which flank the range on the north. Wher- 

 ever veins are observed in the greenstone, they are pinched and 

 barren; but where they enier the compact or granular trap they 

 expand in width, and become charged with metal. This trap 

 has a good degree of firmness, and consists of labrador feldspar, 

 and chlorite. It has been remarked that the best rock in this 

 region for productive veins is neither a crystalline greenstone nor 

 a soft porous amygdaloid, but a granular trap, with occasional 

 amygdules scattered through it, and possessing a good degree of 

 consistency. Where veins enter the greenstone, as before re- 

 marked, they become pinched; where they penetrate the soft 

 amygdaloid, they become scattered and lose themselves. 



The lode of the Cliff mine is seen to occupy a break or de- 

 pression in the hill, and thence can be traced to its base. It was 

 discovered in the summer of 1845, and during the succeeding 

 fall a drift was carried into the greenstone about one hundred 

 feet, and between that point and the summit several others were 

 opened. When first discovered, the vein was only to be seen in 



the upper belt of greenstone, the metalliferous zone being con- 



cealed by detritus. No one could have inferred from its appear- 

 ance at that time that the enormous masses of copper existed 

 but a short distance below which subsequent explorations revealed. 

 ^ * * * At the summit it appeared hardly more than an inch or 

 two in width: the gangue was mostly prehnite, with copper as- 

 sociated with silver; incrusted with beautiful capillary crystals of 

 red oxyd. Further down the vein was again exposed ; here it 

 had expanded to the width of nearly two feet, the veinstone con- 

 sisting of a series of reticulations of laumonite. 



Up to this period the sandstone and conglomerate were sup- 



posed by many to aflTord the best mining-ground, and that to 

 this source they were to look for permanent supplies of the sul- 

 phurets of copper. During the winter of 1845-'46j some Ger- 

 man minerS; in clearing away the talus near the base of the cliff? 



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