Figure F23. A. Close-up photograph of completely altered dunite has experienced substantial brucite alteration. This style of alteration is macroscopically indistinguishable from serpentinization (interval 209-1271A-4R-2, 24–36 cm). B. Photomicrograph showing that brucite forms aggregates of fine, elongate crystals with anomalous, brown interference colors surrounded and interpenetrated by serpentine. This indicates that the brucite has been partially transformed during serpentinization and that brucite formed prior to serpentine (Sample 209-1271A-4R-2, 29–31 cm) (cross-polarized light: blue filter; field of view = 1.4 mm; image 1271A_005). C. XRD spectra for Sample 209-1271A-4R-2, 32

Figure F23. A. Close-up photograph of completely altered dunite has experienced substantial brucite alteration. This style of alteration is macroscopically indistinguishable from serpentinization (interval 209-1271A-4R-2, 24–36 cm). B. Photomicrograph showing that brucite forms aggregates of fine, elongate crystals with anomalous, brown interference colors surrounded and interpenetrated by serpentine. This indicates that the brucite has been partially transformed during serpentinization and that brucite formed prior to serpentine (Sample 209-1271A-4R-2, 29–31 cm) (cross-polarized light: blue filter; field of view = 1.4 mm; image 1271A_005). C. XRD spectra for Sample 209-1271A-4R-2, 32–37 cm, shows prominent brucite peaks.