orks or MKKCURV. 289 



fight yellowish or grayish color, and adamantine luster, translucent 01 

 subtianslucent, crystallizing in secondaries to a square prism. H=l — 

 2. Gr=6'48. It contains 85 per cent, of mercury. 



Iodic Mercury is a still rarer ore from Mexico. Color reddish-brown. 



Selenid of mercury, a dark steel-gray ore, which is wholly evapo- 

 rated before the blowpipe. Occurs in Mexico near San Onofre. 



GENERAL REMARKS ON THE ORES OF MERCURY. 



The mines of Idria were discovered in 1497. The mining is carried 

 on in galleries, as the rock is too fragile to allow of large chambers. 

 The ore is obtained at a depth of about 750 f< et, and is mostly a bitu- 

 ninous cinnabar, disseminated through the rock along with native mer- 

 cury. The latter is in some parts so abundant that when the earthy 

 rock is fresh broken, large globules fall out and roll to the bottom of the 

 gallery. The pure mercury is first sifted out ; the gangue is then 

 washed, and prepared for reduction. For this purpose there is a large 

 circular building, 40 feet in diameter by 60 in height, the interior of 

 which communicates through small openings with a range of chambers 

 around, each 10 or 12 feet square, and having a door communicating 

 with the external air. The central chamber is filled with earthen pans, 

 containing the prepared earth, the whole is closed up and heat is ap- 

 plied. The mercury sublimes and is condensed in the cold air of the 

 smaller chambers, whence it is afterwards removed. After filtering, it 

 is ready for packing. These mines afford annually 5000 cwt. 



The above mode of reduction is styled by Ure " absolutely barba- 

 rous." He observes that the brick and mortar walls cannot be ren- 

 dered either tight or cool ; and that the ore ought to be pounded, and 

 then heated in a series of cast-iron cylinder retorts, after being mixed 

 with the requisite proportion of quicklime, (the lime aiding in the re- 

 duction of the cinnabar by taking its sulphur,) and the retorts should 

 communicate with a trough through which a stream of water passes, 

 for the purpose of condensing the mercury. An apparatus of this kind 

 planned by Ure, is used at Landsberg, in Rhenish Bavaiia. 



The mines of. the Palatinate, on the Rhine, and those of other parts 

 of Germany, are stated by Burat to yield 7.600 quintals. 



The mines of Almaden are situated near the frontier of Estremadu- 

 ra, in the province of La Mancha. They have been worked from a 

 remote antiquity. According to Pliny, the Greeks obtained vermillion 

 from them 700 years before our era, and afterwards imported annually 

 100,000 pounds. The mines are not over 300 yards in depth, although 

 so long worked. The rock is argillaceous schist and grit, in horizontal 

 beds, which are inteisected by granitic and black porphyry eruptions. 

 The mass of ore at the bottom of the principal vein, is 12 to 15 yards 

 thick, and yields in the aggregate 10 per cent, of mercury. It is taken 

 to the furnace without any kind of mechanical preparation. There are 

 many veins in the vicinity, several of which have been explored. The 

 furnaces of Almadenejos are fed almost exclusively by an ore obtained 

 just east of the village, which is a black schist, strongly impregnated 



What is said of the Idria mines 1 How is the ore reduced ? What 

 1» a b«n«i process ? What ii said of the mines of Almaden 1 



