©2 TRANSACTIONS OF THE [Nov..14, 
clase is of the characteristic green, and often shows on massive 
pieces the twinning striations with great distinctness. The 
segregated masses carry other minerals. One in the accom- 
panying collection has a very good crystal of tourmaline, calcite 
and pyrite with it. 
Kyanite occurs over a limited area as stated above. The 
Villard houses, Madison avenue and 50th street, were the oc- 
eusion of bringing much of it to the surface. It is in thin 
blades, and rarely shows a good blue. Prof. Dana has also found 
the allied mineral fibrolite in the region just north. 
Garnets are abundantly distributed through the schist, but 
rarely of good crystalline form. They are then 202. 
In the excavacations at 101st street and Fifth avenue, Mr. 
Slack and myself have found a mineral that we determine to 
be scapolite. It is white or yellowish-white, in large square 
prisms, but somewhat affected by decomposition. I do not 
think it has previously been recorded from the island. 
Magnetite occurs in irregular masses of small size. What I 
have seen is in segregated bunches of quartz. 
Pyrite is quite widely disseminated, but never in very great 
amounts. Dr. Gale attributes much of the disintegration of the 
gneiss to its decay, but I think he overrated its effect. 
Malachite occurs as a green stain in the gneiss about 100th 
street and Madison avenue, but from 6 to 10 feet below the 
surface. It comes from the decomposition of chalcopyrite which 
is very sparsely disseminated through the gneiss. 
2. Granyte.—The most interesting mineral from the granyte 
is tourmaline. It occurs in prisms, often of considerable size, 
everywhere in the upper island. It is very difficult to get out, 
however, as itis extremely brittle. Quite often crystals are 
seen broken acrossand the crack filled up by the matrix. This is 
a fact to be considered in any explanation of the origin of the 
granyte. 
Mica occurs in broad leaves, often six inches and more across. 
Some in the Columbia College collection have dendritic stains 
between the laminz. In some veins the mica is a very delicate 
and beautiful green. 
Orthoclase occurs in large cleavage masses, and rarely in 
crystals. : 
3. Limestone.—Excellent, but somewhat weathered crystals 
of white pyroxene may be dug from the calcareous sand near 
Inwood, and with them are masses of foetid quartz and feldspar. 
4, The products of the decomposition of the gneiss have 
filled its cracks with secondary minerals. Stilbite is quite 
common in red radiated crystals, and its allied minerals, 
chabazite and heulandite, are said to have been found in ex- 
