Htientijic Intelligence — Miscellaneous. 209 



of the " Sattel/' near Niederkirclien, not far from Wolfstein, in Rheuisb 

 Bavaria. These have lately been described by G. Leonhard. One 

 of them is easily explained, viz. when the prehnite assumes the tra- 

 pezoidal form previously belonging to Analcime, an appearance already 

 observed and described by Haidinger. The origin of the other, however, 

 has given rise to vjirious opinions, and its form has been partly attribut- 

 ed to datolite, and partly to stilbite, mesotype, or laumonite. Professor 

 Blum had regarded this variety of prehnite as derived from laumonite, 

 especially as the angles presented great similarity ; and it was only some 

 months ago, when being engaged in a work on pseudomorphoses, he ex- 

 amined the crystals in question with greater attention, that he found the 

 similarity existed only with respect to the sixe of the angles, but not to 

 their position, which is just rcversjcl, in so far as the lateral angles are 

 concerned. As, then, it was thus evident that it could not have been 

 laumonite which had undergone the conversion into prehnite, what 

 substance was it ? The Mineral-comjAoir at Heidelberg, lately re- 

 ceived a quantity of hiumonite from the neighbourhood of Schemnitz, 

 and it immediately struck Professor Blum that the crystals were the 

 same as the pseudomorphic ones, a supposition which was confirmed by 

 measurement. He thus found that this so-termed laumonite was to be 

 regarded as a new mineral ; and the analysis made by Dr Delff shewed 

 that its composition was different from that of the true laumonite. 

 There is, however, a remarkable resemblance between the two sub- 

 stances, both in external appearance, and in many of their properties. 

 The great tendency to decomposition exhibited by laumonite, exists also 

 in this new species, which Professor Blum and Dr Delff propose to term 

 Leonhardite. The crystallographic form is klinorhombic. Primitive form : 

 an oblique rhombic prism, M : M' = 96° 30' and 83^ 30' ; P : M = 114° 

 and 64°. This is the only form observed. The prismatic crystals are 

 frequently aggregated together, so that a large individual is composed of 

 several smaller ones, which are sometimes of equal length, but on other 

 occasions vary in this respect. The lateral planes are streaked in a di- 

 rection parallel to the principal "axis ; two of them are often larger than 

 the others. Sometimes crystalline-columnar and granular masses occur. 

 Cleavage very perfect parallel to the lateral planes, imperfect in the di- 

 rection of P. Fracture uneven. Hardness =3 — 3.5 (in fresh pieces). 

 Brittle, easily frangible. Sp. gr. = 2.25. Translucent on the edges. 

 Lustre pearly, especially on the perfect cleavage -surfaces ; on the frac- 

 tured surface vitreous. Colour white, passing into yellow, and more 

 rarely into brownish. Frequently coated with a brownish or black 

 powder. Streak white. The Leonhardite occurs near Schemnitz, in 

 Hungary, in the fissures and drusy cavities of a trachytic rock ; some- 

 times in considerable quantity. It is also found imbedded, and then 

 imparts a porphyritic structure to the trachyte. The pseudomorphic 

 prehnite above mentioned, undoubtedly owes its form to this mineral. 

 Analyses of the leonhardite have been performed by Dr Delff and Von 

 Babo, and the following are the results. 



VOL. XXXVI. NO. LXXI. JAN. 1844. O 



