THE NATIONAL INSTITUTION- 
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Made or chiastolite is described as being always crystallized in nearly rectan¬ 
gular four-sided prisms. When, however, the end of the prism is carefully ex¬ 
amined, there will be perceived in it a blackish prism enclosed in the larger one, 
which is of a greyish, yellowish, or reddish white color. From each angle of the 
central prism a blackish line passes to the corresponding angle of the outer prism; 
and in each of these external angles there is commonly a small prismatic space, 
filled with the same black matter as that of which the central prism is composed, 
which is a dark clay slate, the same as the rock in which the crystal is im¬ 
bedded. 
As was before observed, Cleveland’s description agrees with this, though, in con¬ 
junction with a figure corresponding to this description, he gives, as another variety, 
I think, a figure of a crystal with a rhombic base, the marking of which agrees 
very well with some of my specimens. I have never found any of these crystals 
rectangular, and but few approaching to that shape. 
In the most perfect specimens, the whole rhomboidal ciystal seems to be en¬ 
veloped in a uniform coat of black, slaty matter, of a very fine grain, and easily 
admitting of considerable polish. When a cross section is made, (and it usually 
breaks in these specimens pretty smoothly,) and the surface ground down and 
polished, it will be seen that this thin black casing encloses a substance of a reddish 
yellow color, of glistening and somewhat foliaceous or sparry appearance, some¬ 
times opaque, sometimes slightly translucent. This yellowish substance encloses a 
smaller hollow prism, of the same blackish matter, marked merely by a thin black 
line, and within it is contained the same reddish yellow matter, as filled the space 
between it and the outer coating; giving, in fact, the appearance of a small pris¬ 
matic crystal, of yellowish matter, with a blackish coat inserted in the centre of a 
larger crystal, of the same color, while small black lines pass from the angles of the 
inner case of black matter, to the corresponding angles of the outer. These black 
lines are very feint and delicate in the transverse diagonal of the crystal; thicker 
and more strongly marked in the longitudinal diameter ; spreading a little as they 
approach the outer casing, so as to give the idea of being formed by a duplicature 
of that investment. In one or two crystals, indeed, this formation is distinctly 
marked. 
In other crystals, less perfect, the bases are more generally rhomboids than 
rhombs. The outer black case is thicker, the yellowish contained matter less regu¬ 
lar in its figure, (the angles being rounded off,) and, instead of an inner crystal re¬ 
sembling the outer, it is divided, by transverse diagonals of the black matter, into 
four portions. In some specimens these are very small, appearing on the section 
merely like dots, while the bulk of the crystal is composed of the blackish coat, 
which in these is rather grey than black. In other instances there is no regular 
figure to the contained matter, but it is dispersed through a black crystal, in irregu¬ 
lar patches, giving to the section a mottled appearance. 
Although the disposition of the separate parts differs from the description, I have 
looked upon these two varieties as made, but of a different variety from that com¬ 
monly described. Yet it is among the second variety that I have found very good 
specimens of the intersection of crystals forming a cross. 
In a third variety, there is no yellowish contained matter to be distinguished. 
The crystals consist wholly of blackish or grayish matter, sometimes with and 
