good crystals on hornblende schist at the Speedway and 165th Street.
Allophane, hydrous aluminum silicate, given by S. C. H. Bailey and Chamberlin as found in " silvery white incrustations."
Amphibole.—(See Actinolite, Hornblende, Tremolite, As-bestus, Anthophyllite, etc.)
Amethyst, purple quartz, rare, taken in 59th Street, 6th and 7th Avenues, perhaps from bed of quartz at 117th Street near 4th Avenue.
Amianthus, in serpentine boulders Amity Street, and in West 58th Street; confounded probably with chrysotile, which is a fibrous serpentine.
Analcite, rare,
101st Street and 5th Avenue, tetragonal trisoctahedrons coating small
cavity in hornblende gneiss, with chabazite. It is a hydrous silicate
of sodium and aluminum.
Anthophyllite (hydrous), tremolite-like, gray-brown, radiating acicular mineral distributed in drift, a changing and hydrous amphibole.
Apatite, the
phosphate of calcium, is often found in attractive green crystals,
though usually broken in extraction; white crystals are also mentioned
by Bailey; developed in granite veins, good dark crystals in quartz, at
Fort George, at 120th Street and 5th Avenue; crystals showing
hemihedrism from 43d Street and 1st Avenue; not uncommon.
Apophyllite, hydrous silicate of calcium and potassium, drift in trap boulder. (Bailey.)
Aquamarine (gem beryl), light green, translucent, from Manhattanvilk; rare.
Aragonite, carbonate
of lime, in thin veins, columnar in form, in dolomite from Morrisania,
in the Bronx; taken at 4th Avenue and 96th Street.
Asbestus, hair-like
fibres thinly strewn over or through schist, at 14th Street and 5th
Avenue, also in broad sheets of fibres from Spuyten Duyvil (Hall of
Geology, American Museum Natural History).
Autunite, hydrous
phosphate of uranium and calcium, in scale on quartz in granite,
invading the mica sheets, and possibly interleaved with them; yellow.
Azurite, carbonate of copper, in spots and stains on hornblende schist; oxidized chalcopyrite.
Basanite, (?) in drift; the touchstone of jewelers; a dark chert.
Beryl, silicate of aluminum and beryllium, not uncommon,
