desilicated

Such a digested, kaolinized, desilicated rock as we would naturally look for we find in the porphyry _near the contact_; and its condition there, so different from what it is remote from the contact, seems to indicate an exposure to local and decomposing influences, such indeed as a hot chemical solution forced up from below along the plane of contact would furnish.

Scientific American Supplement, No. 446, July 19, 1884 Various