Mr, Brooke 07i Haydenite a?id Couzeranite. 175 
able to show, in each case, that my original views have been 
supported by a careful re-examination of the facts. 
Dublin, January ] 7, 1 840. 
XXXI. On Haydenite and Couzeranite, By H. J. Brooke, 
Esq,, F,R,S,^ 
I N the last Number of the Phil. Mag. p. 156, I observed a 
notice of a new mineral (Beaumontite) which M. Levy has 
found accompanying Haydenite, a mineral that is said to 
occur near Baltimore in the United States ; and M. Levy 
remarks that I have classed Haydenite with Heulandite 
without assigning any reason for so doing. 
I did so from perceiving that the small and brilliant yel- 
lowish crystals on the specimen I examined resembled Heu- 
landite, in having a nacreous plane in only one direction, cor- 
responding with the P of W. Phillips (Mineralogy, p. 39. 
Ed. 1823); in the form, as far as I could distinguish it in 
the minute and closely aggregated condition of the crystals ; 
and in the near agreement, about 112% of the angle between 
the nacreous plane and a plane appearing to correspond with 
the a of W. Phillips. 
M. Levy is doubtless aware of a variety of Heulandite 
found at Arendal, of a brown or yellowish brown colour, 
in small bright crystals, and accompanied by stilbile in glo- 
bularly-radiated concretions of a dull yellowish colour. The 
specimen sent to me from America as Haydenite has a similar 
accompaniment of stilbite of the same description, and this 
circumstance tended to confirm my impression that Hay- 
denite was Heulandite. It is probable, therefore, that the 
specimen sent to me from America as Haydenite, is really 
not that mineral, and I do not find anything like M. Levy’s 
Beaumontite upon it, except that the crystals are small and 
brilliant, and of a pearly lustre. ” Mr. L. does not say on 
what faces this lustre appears in Beaumontite. 
I find I have been formerly led into an error relative to Cou- 
zeranite by specimens received from Paris, by Mr. Heuland, 
from Mr. Pentland. On examining the crystals I found them 
to be felspar, and I accordingly stated, on the faith of the 
specimens so transmitted to Mr. Heuland being genuine, that 
Couzeranite was only felspar. I have since seen other speci- 
mens named Couzeranite in apparently square prisms, and if 
these are the true mineral it has no resemblance whatever to 
felspar. 
H. J. B. 
* Communicated by the Author. 
