114 
The position chosen to show most of this specimen 
gives it a very strange appearance, especially as so many 
crystals are situated very close to each other. 
The lowest geometrical figure exhibits the position of the 
nucleus. . 
The matrix is partly composed of very small crystals 
of Feldspar, and partly of columnar Quartz crystals, 
with some irregular six-sided facets, forming the pyramids 
common to Quartz, which, in these, are often more 
transparent within than externally, giving them an opaque- 
coated appearance, depending perhaps on the water of 
crystallization. 
Feldspar is in its forms extremely puzzling, but ea 
be well understood, as we shall be the more likely to know 
it, if occasion requires, without analysing it, which will 
facilitate our inquiries into so important a substance, 
often so very useful in porcelain manufactories.—See 
tab. 211, 212, and 213. 
