Mr. Brooke on Haydenite and 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 17,1840. 



XXXI. On Haydenite and Couzeranite. By H. J. Brooke, 

 E&q., F.R.S.* 



T 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 stilbite in glo- 

 bularly-radiated concretions of a dullyellov^'ish colour. The 

 specimen sent to me from America as Haj'denite 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. 



