Geology of the Braden Mines:

Here is a report explaining the basic geology of the Braden mines and something about the mine layout as well. I emphasized certain points of particular interest with yellow highlight: 

(Some images can be clicked for a larger view)

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Andesite is described as a relatively pale rock with porphyritic texture.  It occurs in lava flows and stocks together with basalt, latite and trachyte.  It is the most important volcanic rock after basalt, with the distinction made according to the color index. In andesite the dark minerals make up less than 40 per cent by volume of the total rock whereas in basalt, the dark minerals exceed 40 per cent.

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Andesite rock samples:

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A ridge of Andesite lava flow:

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NOTE ALSO: Reference to the use of  22-ton underground ore cars in groups of 14 !  The ones used at Kennecott & the  Kennecott Beatson-Girdwood Mines on LaTouche Island, Prince William Sound,  were 3 and 4 ton cars.