Congrès géologique international, Congrès géologique international… (1891)
“ Very nearly as conspicuous are great masses of a porphyritic rock, including large and perfectly developed crystals of feldspar, chiefly of the triclinic varieties, the whole resembling the more extreme forms of laccolitic rocks, the habitus of which is now recognised as being very distinctive. But these porphyries have been altered by metasomatic changes, the nature of which has not been at the present time elucidated. Many masses of peridotite are also found, and these are generally much altered, and often completely changed into a greenish-black serpentine. ”
