Experiments on Allanite. 279 
About a year ago, Mr. Allan, who has greatly distin- 
guished himself by his ardent zeal for the progress of mi- 
neralogy in all its branches, favoured me with some speci- 
mens of this curious mineral, and requested me to examine 
its Composition,—a request which [ agrecd to with pleasure, 
. because J expected to obtain from it a quantity of yétria, 
an earth which [had been long anxious to examine, but had 
not been able to procure a sufficient quantity of the Swedish 
gadolinite for my purpose. The object of this paper is 
to communicate the result of my experiments to the Royal 
Society,—experiments which cannot appear with such pro- 
priety any where as in their Transactions, as they already 
Contain a paper by Mr. Allan on the mineral in question. 
I. Description. 
I am fortunately enabled to give a fuller and more accu- 
rate description of this mineral than that which formerly 
appeared, Mr. Allaw having, since that time, discovered an 
additional quantity of it, among which he not only found 
fresher and ivetter characterized fragments, but also some 
entire crystals. In its composition it approaches most 
nearly to cerite, but it differs from it s0 much in its exter- 
nal characters, that it must be considered as a distinct 
species. I have therefore taken the liberty to give it the 
name of Allanife, in honour of Mr. Allan, to whom we are: 
in reality indebted for the discovery of its peculiar nature. 
Allanite occurs massive and disseminated, in irrecular 
masses, mixed with black mica and feldspar ; also crystal- 
lized: the varieties observed are, 
1. A four-sided oblique prism, measuring 117° and 63°. 
2. A six-sided prism, acuminated with pyramids of four 
sides, set un the two adjoining opposite planes. These 
last are so minute as to be incapable of measurement. 
But, as nearly as the eye can determine, the form re- 
sembles Fig. 3, Plate VI; the prism of which has two 
right angles, and four measuring 135°. 
3. A flat prism, with the acute angle of 63° replaced by 
one plane, and termmated by an acumination, having 
three principal facettes set on the larger lateral planes, — 
with which the centre one measures 125° and 55°. O 
this specimen, an engraving is given in the Plate, Fig. 4. 
Specific gravity, according to my experimetits, 3-533. 
The specimen appears to be nearly, though not absolutely, 
pure. This substance, however, is so very much mixed 
with mica, that no reliance can be placed on any of the 
trials which have’ been made. Count Bournon, surprised, 
S4 at 
