Browse Items (1651 total)

Quartz and feldspar appear to be shattered

Chlorite, epidote, and mica are present as secondary minerals

Mostly quartz, oligoclase, and microcline

Gabbro associated with syenite ring dike near Concord, North Carolina

Mostly plagioclase and biotite

Shows considerable fracturing, thin section examination shows ophitic texture

Ophitic texture in thin section, plagioclase exhibits some alteration to sericite

Ophitic texture in thin section, some opaques

Ophitic texture in thin section, some opaques

Quarred for monumental stone, ophitic texture in thin section, minor amount of opaques

Plagioclase altered to epidote and flaky sericite, rock has undergone slight metamorphism

Much of the plagioclase has been altered to epidote and sericite, hornblende occurs as long prismatic crystals arranged in sprays

Some alteration has produced epidote, most of the hornblende is prismatic and occurs in two colors

Fedlspar is cream-pink colored and much has been altered to sericite/epidote

Rock may have undergone some alteration

Amphibole, epidote, chlorite, quartz, calcite, and clinozosite present are thought to be alteration products

Rock appears to be hydrothermally altered, sample is taken from a sill and is source of basaltic tuffs in area

Contains biotite, orthoclase, hornblende, quartz, and titaniferous magnetite

Rock has been subjected to alteration and shear forces, the garnet present is probably an alteration product