Notice of Minerals from Neio Holland. 161 



being usually of nearly the same size. Color, pure white ; lustre 

 of P, pearly ; secondary planes a,/, vitreous ; bnt the faces M, T 

 possess a dull, waxy, or opalescent lustre, which I have not before 

 observed in the crystals of this mineral, apparently, however, con- 

 fined to the surface ; and the same faces are more or less curved 

 or hollowed, so as not to admit of measurement by the goniome- 

 ter. Some of these faces form a regular uniform curve, inclining 

 equally towards the terminal planes P, obliterating the small re- 

 placements a, /, which are usually very distinct. 



Stilbite. (Prismatoidal Kouphone-spar, M.) — The crystals 

 generally are not well defined, the masses consisting of pure 

 white pearly folia, forming sheafs or fasciculated groups, showing 

 at their free extremities, only imperfect crystalline faces of a low 

 pyramid, inclining from the solid angles of the prism. Some of 

 these masses, composed entirely of the stilbite, are of a globular 

 form, presenting on fracture, a radiation of fibres from a common 

 centre. A few small, but very brilliant, and perfectly transpa- 

 rent crystals of this mineral, were however seen in some of the 

 vesicular cavities of the amygdaloid, exhibiting the pri- 

 mary prism, compressed into low six-sided tables, the 

 four replacements at the summits of the prism being 

 narrowed down so as to form regular beveled edges upon 

 the four corresponding sides of the tables, producing a 

 form nearly similar to Fig. 6, taken from the System of 

 Mineralogy hj Beudant, Vol. 2d, plate x, fig. 62. 



Mesotype of Phillips. (Peritomous Kouphone-spar of Haidin- 

 ger.) — A nest of the crystals of this mineral was met with in the 

 form of small implanted individuals, occupying the cavity of a 

 mass of quartz and chalcedony. They are in elongated rhombic 

 prisms, colorless, transparent, and of a glassy lustre; but a few 

 of them have a silky, fibrous appearance, similar to some of the 

 specimens met with in the more ancient lavas of Vesuvius. They 

 do not form groups of united, divergent crystals. 



Rhotnbohedral Quartz. — I was so fortunate as to find among 

 this collection, besides several of the sub-species of this mineral, 

 two or three specimens exhibiting the primary obtuse rhomboid 

 in great perfection, and of considerable size ; some of them mea- 

 suring half an inch" across their planes. They present highly 

 polished surfaces, are transparent and colorless ; and it is evident, 



Vol. XXXIX, No. 1.— April-June, 1840. 21 



