EXPLANATION OF PLATE XXVI.

A (one nicol). Lamellar structure; quartz chalcedony, and adularia pseudomorph after replaced calcite. Jarbidge, Nev. (X 18.)

B (x-nicols). “Radial” quartz structure; probably pseudomorph after calcite. Republic, Washington. (X-)

C (x-nicols). Anomalous replacement quartz normal to pyrite veinlet. Oak Run prospect, Shasta Co., Cal. (X 55.)

D (x-nicols). Anomalous replacement quartz in pyritized schist. (Thin section lent by C. F. Tolman, Jr.) Campo Seco, Cal. (X 36.)

E (one nicol) and F (x-nicols). Inclusional pattern by strain; twinning by gliding (?). Union Hill Mine, Grass Valley, Cal. (X 104.)

EXPLANATION OF PLATE XXVII.

A (x-nicols). “Shredded” quartz by pressure. Cobar, Australia. (X 35.) B (x-nicols). Recrystallization by stain of single quartz crystal. Sons of Gwalia Mine, W. Australia. (X 47.)

C (x-nicols). Subhedral recrystallization quartz; loss of inclusions by strain. (Largest Remnant is x.) Boulder Deep Levels, W. Australia. (X 66.)

D (x-nicols). Complete recrystallization in ribbon quartz. Sons of Gwalia Mine, W. Australia. (X 39.)

E (one nicol) and F (x-nicols). Recrystallization in grid pattern; loss of inclusions. Kennedy Mine, Jackson, Cal. (X 142.)