372 On ALLANITE, a new 
its branches, favoured me with fome {pecimens of this curious 
mineral, and requefted me to examine its compofition,—a re- 
queft which I agreed to with pleafure, becaufe I expected to 
obtain from it a quantity of yttria, an earth which I had been 
long anxious to examine, but had not been able to procure a 
fufficient quantity of the Swedith Gadolinite for my purpofe. 
The object of this paper, is to communicate the refult of my ; 
experiments to the Royal Society,—experiments which cannot 
appear with fuch propriety any where as in their Tranfac- 
tions, as they already contain a paper by Mr ALLAN on the mi- 
neral in queftion. 
I. DeEscRIPTION. 
{ am fortunately enabled to give a fuller and more accurate 
defcription of this mineral than that which formerly appeared, 
Mr Atzuan having, fince that time, difcovered an additional 
quantity of it, among which, he not only found frefher and 
better characterifed fragments, but alfo fome entire cryftals. In 
its compofition, it approaches moft nearly to Cerite, but it dif- 
fers from it fo much in its external characters, that it muft be 
confidered as a diftiné fpecies. I have therefore taken the li- 
berty to give it the name of Allanite, in honour of Mr Auuan, 
to whom we are in reality indebted for the difcovery of its pe- 
culiar nature. 
ALLANITE occurs maffive and diffeminated, in irregular 
maffes, mixed with black mica and felfpar; alfo cryftallifed ; 
the varieties obferved are, 
1. A four-fided oblique piifm, meafuring 117° and 63°. 
2. A fix-fided prifm, acuminated with pyramids of four fides, 
fet on the two adjoining oppofite planes. Thefe laft are 
fo minute as to be incapable of meafurement. But, as 
nearly as the eye can determine, the form refembles 
Fig. 1.3; the prifm of which has two right angles, and 
four meafuring 135°. 
