Browse Items (41 total)

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

Exhibits a runic texture, the kind that is found in feldspar mining operations (undesirable due to high amount of quartz)

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

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

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

Rock may have undergone some alteration

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

Contains inclusions of relict gabbro

Contains secondary products of alteration including serpentine, talc, chlorite, carbonates, and iron oxides

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

Mostly plagioclase and biotite

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

Ophitic texture in thin section, some opaques

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

Shows considerable fracturing, thin section examination shows ophitic texture

Biotite is variable in amount, but it is always evenly distributed

Sample comes from flow rocks that are associated with lithic fragment tuffs, pyroxene and chlorite are present as an interstitial material

Contains augite, amphibole, plagioclase, ziron, opaques, and a fine-grained alteration product (unknown)

Mined and marketed under the name "Aplite"