CRYSTALLOGRAPHICAL EXAMINATIONS. 
513 
about tV in diameter and thick, with brilliant pearly and adamantine lustre on the 
faces of the tables ; no other brilliant planes could be perceived. It is hard ; scratches quartz, 
but does not topaz or spinelle. It is transparent to translucent, and sometimes nearly opake. 
When transparent, it is of a light rose-red; when translucent, reddish grey. Cleavable in 
one direction (that of the planes of the tables). Cross fracture uneven and splintery, with a 
shining lustre. 
It is infusible either per se, with borax, carbonate of soda, or with microcosmic salt. With 
microcosmic salt the glass became yellowish when hot, after having been long heated, bnt was 
colorless when cold, and the particle of mineral did not appear to have been diminished in size, 
or to have dissolved in any perceptible degree in the flux. 
4. YOUNGITE, (so called,) of Amity. SCAPOLITEI 
Crystals sent me in 1832. It occurs crystallized and massive, in the white limestone of 
Amity, New-York. It scratches glass, though impressible with a knife. Color is grey and 
brownish grey, occasionally with a scarcely perceptible tinge of red. Before the blowpipe, on 
a platinum support, at a high heat, fuses with some intumescence, and an intense glow like 
lime, into a translucent white or grey globule. Borax being added, does not dissolve all, a 
skeleton remaining, and the highest heat that could be raised produced no additional effect. 
It has many of the characters of scapolite. The crystals were not brilliant, but the planes 
were smooth. The following measurements were made with the common goniometer : 
Fig. 31. 
> 
a on h . 
. 147°00' 
X 
~~l - 
/ 
h on e . 
. 106 10 
The cleavage planes are pa¬ 
c on d . 
. 149 00 
rallel to d and d'. Some of the 
^ d 
e 
i 
c on e . 
. 90 00 
angles correspond nearly with 
d on e . 
. 123 00 
augite and scapolite. 
d on/ . 
. 116 30 
5. PARGASITE, BLENDE and RUTILE, of Amity. 
From the specimens of pargasite obtained at Amity, I procured some small fragments with 
faces. When measured with the reflective goniometer, they gave constantly for the angles of 
the primary form 124° 30' and 55° 30'. Prof. Shepard has thought this mineral to be cocco- 
lite, but these angles are different from those of augite. 
In the same mass was found a great number of minute crystals of blende, as is inferred 
from their cleavage, infusibility, lustre, and angles of 120° and 125° 15', indicating planes of 
the rhombic dodecahedron and regular octohedron. 
Minute red brilliant prisms with an adamantine lustre, were also observed in this pargasite. 
They were supposed from their aspect to be rutile, but no experiments were made. 
Geol. 1st Dist. 65 
