PHYSIOGRAPHY. 



Leadhillite. 



Cleavage, parallel to o, and traces parallel to a. Frac- 

 ture conchoidal, scarcely observable. Surface o very 

 smooth and even ; some of the faces curved or uneven. 



Lustre resinous, inclining to adamantine, pearly upon o. 

 Color yellowish white, passing into various, pale grey, green, 

 yellow, and brown tints. Streak white. Transparent . . . 

 translucent. 



Rather sectile. Hardness =2-5. Sp. gr. =6-266. 



Compound Varieties. Twin-crystals, frequent. Mas- 

 sive : composition lamellar, or granular. 



1. Before the blow-pipe, this mineral first intumesces a little, and 

 then becomes yellow, but re-assumes a white color on cooling. It effer- 

 vesces briskly in nitric acid, and leaves a white residue. 



2. Analysis. 



By BERZELIUS. 



Carbonate of lead . . . . . . . 71*1 



Sulphate of lead 30-0 



With traces of muriatic acid, giving an excess of !!, probably owing 

 to the existence of a subsalt of lead in the mineral. 



3. It occurs principally at the Lead Hills of Scotland, in a vein trav- 

 ersing grey wacke, accompanied with various other ores of lead : it has 

 been brought from Spain under similar circumstances. 



LEELITE. 



Massive. Fracture splintery. Lustre and translucency like 

 horn. Sp.gr. =2-71. 



1. Analysis. 

 By MITCHELL. 



Silica 81-91 



Alumina . 6'55 



Protoxide of iron . 6-42 



Potash 8-88 



2. The specimens were brought from Gryphytta in Westmania, Swe- 

 den. 



3. It scarcely admits of a doubt, that the Leelite is a variety of Feldspar. 



LENZINITE. 



An impure variety of Opal, in a state of partial decomposition. 



