318 
DESCRIPTIVE MINERALOGY. 
St. Lawrence County. Spinelle of a light blue colour, and having the primary form, 
occurs associated with chondrodite, about two miles north of the village of Somerville in the 
town of Rossie. The crystals, however, are quite small. 
It is a singular fact, that while spinelle is so very abundant in various parts of Orange 
county, it should be so rarely met with in the similar formations in the northern parts of the 
State. Although it is found in the counties of Jefferson and St. Lawrence, and, according to 
Dr. Emmons, also in the counties of Essex and Warren, the crystals are often minute, and 
always, as hitherto observed, sparingly disseminated ; so that it may be still said to be rare 
in Northern New-York. 
APPENDIX. 
Soft. Spinelle. There is a mineral found in the town of Warwick in Orange county, which 
is of a black colour, and has the crystalline form of spinelle. It is imbedded in a gangue 
of dark coloured soft serpentine. The octahedral crystals are so soft that they can be easily 
scratched with a knife, and reduced to a coarse powder; but the powder, which is of a grey 
colour, is gritty, and is with difficulty rendered impalpable. 
This mineral has passed under the names of kerolite pseudomorphous of spinelle, pseudo- 
lite, etc., which have been employed to express the supposed chemical constitution and the 
crystalline form. 
In conducting the analysis of this mineral, I found that a large proportion of the powder 
resisted two or three ordinary fusions with carbonate of soda. This led me to suspect that it 
might contain a portion of real spinelle, instead of its being, as I had supposed, entirely 
made up of serpentine or some similar mineral. The correctness of this view was confirmed 
by subsequent examinations. 
The composition of these crystals is nearly as follows, viz: 
Silica,. 19.07 
Alumina,. 35.00 
Oxide of iron,. 9.97 
Magnesia,....„. 28.58 
Water,. 7.33 
If now we take about 17 parts of the silica, 15 of magnesia, 6 of water, and 2 of oxide of 
iron, they will produce about 40 per cent, of serpentine, and the remaining constituents will 
be nearly in the proportion in which they are found, according to the most trustworthy ana¬ 
lyses, to occur in spinelle. 
The peculiarity of these crystals is therefore to be referred to the intrusion of the serpentine 
into the crystals of spinelle, a part of which has been removed. And although the crystals 
are softer than might be supposed from their composition as above stated, it is quite probable, 
that during the process of substitution, the cohesion of all the particles has been impaired, 
so as to bring about the apparent softness of the crystals, while the particles are really so 
hard, as they prove to be when subjected to the action of the pestle. 
