1822.] Br. Clarke on Cadmium, 127 



radiated structure, like waveilite. The second is a grey stalactite 

 body, externally resembling chalcedony, and appears in cavities 

 as if the substance, like tallow or wax, had been melted and 

 flowed over the surfaces of those cavities. The third is an 

 earthy, or arenaceous body, of an orange-brown colour, wholly 

 soluble, with the mosthvely effervescence, in muriatic acid. All 

 these contain rather less than one per cent, of i:ar donate of cad- 

 mium ; insomuch that when the mineral has been triturated and 

 exposed w^on platinum foil to the action of the blue fame hef ore 

 the blow-pipe, the proof of the presence of cadmium is made 

 instantly apparent by the test already mentioned. 



In the same cave where this carbonate is found, there is found 

 another mineral, called also Calamine, which is cadmiferous ; but 

 which instead of being, like the former mineral, a carbonate, is a 

 silicate of zinc. This occurs more reirely, but the mineral is 

 crystallized, and very pure, a^d gelatinizes in muriatic acid, in 

 the most perfect and transparent manner, being slowly soluble 

 in that acid without any effervescence.* This mineral presents 

 an aggregation of small crystals, whose forms cannot distinctly 

 be ascertained. Externally it is of a grey colour, and when 

 broken, the interior of the crystals exhibits the sort of radiated 

 or stellar structure, which characterizes one variety of the car- 

 bonate; and the two minerals so much resemble each other in 

 this respect, and in their lustre and colour, that they may easily 

 be confounded. The specific gravity of the silicate estimated in 

 pump water at the temperature of 50° of Fahrenheit equals 3" 10. 



Possibly all the Derbyshire carbonates of zinc may contain 

 cadmium, as well as some of the silicates. This metal appears 

 to me to be so decidedly present in many of the ores used in our 

 manufactories that I have reason to beheve it exists also in the 

 zinc manufactured from those ores ; for if a little sheet zinc be 

 scraped with a knife, and the powder placed upon charcoal or 

 vl^ow platinum foil, and expos-ed to the blowpipe, ihe appearance 

 of the *' anneaujaune, ou orange, dioxide de cadmium," mentioned 

 by Berzeliusf as a test of the presence of the metal is easily 

 manifested. This is a matter which may soon be confirmed or 

 contradicted by a regular chemical examination of the zhic of 

 commerce. 



Other carbonates of zinc containing cadmium are those of 

 Mendip, in Somersetshire, of a dark grey colour, investing cavi- 

 ties, as a stalactite, in masses otherwise of a reddish-brown hue. 

 I have not been able to detect any of this metal in the carbonates 

 of zinc from Holywell, in Flintshire. The specimens which I 

 examined were stalactites, which had coated over the crystals 

 of other bodies, and destroyed them ; appearing in hollow pseu.- 



* It was found in the Cumberland Cave as before mentioned, by Prof. Sedgwick. 

 f See a former note. 



