1832.] Examination of Minerals from Ava. 15 



may be called from its behaviour with tests : the colour of the latter is 

 greyish white, with greenish yellow imbedded nodules : before the blow- 

 pipe it is unalterable, but it hardens so as to scratch glass easily : it 

 effervesces strongly with nitric acid, and leaves a silicious residue : the 

 solution lets fall a small precipitate with sulphate of soda, and a more 

 copious one with ammonia and phosphate of soda. 



2. — Small hexagonal plates of Mica ; splitting into thin plates of a 

 dark-brown colour : non-elastic : heated on charcoal, they assume a 

 golden colour from the separation of the plates : with a stronger heat they 

 fuse into a black enamel : resembles Hauy's Mica annulaire. 



3. — Crystallized and anhydrous Gypsum. 



4. — Dark green prismatic Hornblende ; obliquely hexahedral, with 

 rhomboidal cleavage : — fuses with difficulty into a black enamel. 



Metallic Minerals. 



5. — Quartzy Malachite; of a light-green colour : by digestion in 

 boiling nitric acid this mineral yielded 18J per cent, of oxide of copper. 



6. — Black oxide of Manganese ; fracture dark grey, granular, earthy : 

 exterior surface shining black and mammellated ; with borax, in the 

 blow-pipe flame, gave a peuce coloured glass, discriminative of manganese. 



7. — Pisiform oxide of Iron — in dark-brown balls of the size of peas: 

 exhibiting a stellated structure on fracture : before the blow-pipe, and 

 cupellated with lead, proved to be almost entirely composed of red 

 oxide of iron. 



8. — Argentiferous Galena — from "a newly discovered mine near 

 Ava: yielded on analysis i per cent, of silver, with slight contamination 

 of copper and zinc. 



9. — Crystallized oxide of Lead or Litharge. — This mineral is believed 

 to be new, at least it is not described in any catalogue of the ores of 

 lead, which have been consulted. 



The specimen resembles yellow micaceous schist in general appear- 

 ance : it is composed of a confused aggregation of micaceous crystals 

 of a pink-yellow colour : the interstices in some places filled with yellow 

 earthy litharge : — and the exterior of the nodule coated with white 

 carbonate of lead. 



The analysis was effected by solution in nitric acid, and preci- 

 pitation by sulphate of soda, which yielded 133,5 grs. of sulphate, 

 equivalent to oxide of lead 99. 



Prussiate of potash proved the existence of copper and iron, 

 weighing 1 . 



100. 



