071 the Lead Mines of the Sierra de Gador. 56^ 



by porphjTies, trachytes and basalts, which are stated to present 

 very singular phsenomena. Gneiss projects above the tertiary strata 

 in many places. 



The paper was accompanied by specimens of galena, of which the 

 following analyses are given in the paper itself: — 



Specimen, No. 1 70*8 percent. Lead l"05per cent. Silver Ifioz.pergal. 



2. Radiated 62-1 0-65 lOi^ — 



3. Black ... 22'25 0-325 5,| — 



About 400 tons of numbers 1 and 2, have been extracted from 

 the mine during the months it had been worked ; and the produce 

 about the time the paper was written was fifteen tons a day. 



A notice on the Sierra de Gador, and its lead mines, by Josias 

 Lambert, Esq., F.G.S. 



The Sierra de Gador, celebrated for its lead mines, is situated be- 

 tween the Sierra Nevada and the Mediterranean. Its length from 

 west to east is nearly forty miles ; its breadth varies from five to 

 ten miles, and its highest point, — the Collado de los Valientes, 

 near its western extremity, — is upwards of 6000 feet above the sea. 

 From that point eastward, the height gradually decreases till it 

 is reduced near the Almeria to the level of that river. The 

 southern face is precipitous, and from its base to the Mediterranean 

 extends the tertiary plain of Dallas. The western flank is also pre- 

 cipitous, but the northern face rises more gently from the river Al- 

 meria, which separates the Sierra de Gador from the Sierra Nevada. 



The principal mass of this range of mountains is composed almost 

 exclusively of a limestone, considered by Mr. Lambert to belong to 

 the lowest of the transition rocks, because its stratification is in 

 general conformable to that of the nucleus of the Sierra Nevada, 

 and because it is believed to contain no organic remains. It is of a 

 grey or dark colour, and of a compact or finely grained texture, but 

 it is sometimes, though rarely, friable. It passes doviTOwards by 

 alternations and transitions into clay-slate, talcose or mica-slate, 

 and in the upper part, it is connected with breccias and limestone 

 conglomerates. 



The limestone is generally traversed by veins of calcareous spar 

 and fluor spar, frequently so arranged as to resemble the stripes in 

 the skin of a zebra. It is also occasionally magnetic, on account of 

 disseminated particles of magnetic iron. The stratification is regu- 

 lar in some places, but it generally presents great inflexions and 

 disruptions, and curves of a thousand diflFerent natures. The pre- 

 vailing strike of the beds is from east to west, but from the western 

 base of the mountain at Castala to near the highest point in the 

 Loma del Sueiio and Collado de los Valientes, it is from north to 

 south. The inclination of the beds varies very much both in direc- 

 tion and inclination ; the former being sometimes south, but often 

 north, and occasionally cast; and the latter difl^ering from 15° to 

 45°. The beds are for tlie greater part compact, but the higher 

 consist of a breccia, mixed with slate-clay and clayey ochres. The 

 stratification in these beds is sometimes well pronounced, and at 

 2 2 



