300 Alger's Localities of Rare Minerals, 
countries. Now one of my specimens, from New York, has 
the distinct form of Chabasite (the perfect rhombohedron,) and 
of Phacolite (perfect double six-sided pyramids.) The first 
form, however, is rare; the incipient replacements are also 
shown ; but these crystals have not the full perfection of waxy 
lustre reflected by the ultimate form of Phacolite, —a singular 
effect, attributable, probably, to the nature of the solvent in 
which the molecules were suspended. 
Approach of twin-crystals to the Phacolite form. These, 
as they are sometimes presented, would, unless carefully exam- 
ined, be mistaken for the true form of Phacolite. The most 
perfect specimens I have seen, are from Nova Scotia. They 
consist of two rhombohedrons united in the usual manner, 
each crystal turned half round, but having their superior edges 
and lateral angles deeply replaced. The approach to the form 
of Phacolite is thus produced : the edges and angles not stand- 
ing out in relief, as they ordinarily do in these twin forms. 
The strize, parallel with the edges of the two rhombohedrons, 
so intersect as to show the compound nature of the crystals. 
Dr. C. T. Jackson has a fine specimen of this variety from the 
Two Islands, in Nova Scotia, of a wine-yellow color; I have 
another pure white, from the same place. 
Yitro-cerite. This rare mineral is found, associated with 
Brucite, in rolled masses of limestone, in the town of Amity, 
Orange county, New York. I have, as yet, seen sanción 
specimens of it, which I found among some fragments of lime- 
stone containing Brucite and mica, in the duplicate collec- 
tions belonging to the late Dr. Horton, of Edenville. It at- 
tracted my attention as being unlike fluor spar, which it was 
supposed to be at the time, and I have now satisfied myself 
that it is Yttro-cerite, though I have not gone so far as to 
detect the Yttria, the presence of which in the mineral cannot 
be indicated by mere blowpipe experiments alone. It has n° 
crystalline structure, but appears in thin layers, or seam? 
which sometimes amount to scarcely anything more 
