242 Description and Anali/sis of Erlan. 



strata of a I'ed felspar, almost as small and fine-granular as erlan 

 usually is, but it may be immediately distinguished from that 

 substance by its inferior specific gravity, which is 2-6. The 

 mountain consisting of erlan, and a small quantity of mica, 

 wiiich are also mixed with slate, and which aggregate I call 

 Erlan-rock, constitutes a portion of at least 100 fathoms in 

 width, in the chain of the Erzgebirge, that separates the Piihle 

 from the Schwarzwasser. The stratification is here inter- 

 sected by small parallel veins of prehnite, associated with 

 fluor-spar, blackish-green radiated hornblende, green augite 

 (sahlite), green epidote, copper-pyrites, copper-green, &c. The 

 prehnite of this place, of a greenish-white colour, and partly 

 crystallized in tlie well-known tabular prisms of 103°, was 

 taken for quartz: it is remarkable that here, as almost every 

 where else, it is accompanied with copper ore. In the pre- 

 ceding year erlan was found at the Teufelstein, below Schwar- 

 zenberg, but only in a compact state. I have been assured 

 that it is found in the Fliissegruben near Breitenbrunn. 



The name Eiian refers to the place where it was first found, 

 near the village and forge of Erla, and it may be taken as a 

 temporarj' one, until the crj'stalline nature of the mineral be 

 studied. I doubt not (as it is crystallized) but that some 

 coarse-granular erlan may be found, which will show the di- 

 rection of the cleavage better than the varieties hitherto dis- 

 covered. All doubts respecting its identity as a mineral 

 species would then be dissipated. I know no mineral, how- 

 ever, which can be easily mistaken for erlan. It most resem- 

 bles gehlenite in oryctognostic characters; it is soon distin- 

 guished from felspar by its greater weight, and from saussurite 

 (or dyskolite) by its inferior weight and hardness. 



I heard that this flux is roasted before it is used ; and that, 

 for the smelting of iron ore, at Erla they mix it with an equal 

 quantity of wliite granular limestone. 



My highly esteemed friend Professor C. G. Gmelin, at my 

 request, was so kind as to subject erlan to a minute chemical 

 examhiation. 



Chemical Examination of Erlan ; by Professor C. G. Gmelin, 

 of Tiibingen. 



A. 



The specific gravity of the purest foliated erlan, determined 

 at the temperatu''e of 5^-H Fahrenheit, was 1'7507.* The 

 S})ecimen employed weighed 28 grammes. 



* There must be an error here, periiaps in writing only, as the specific 

 gravity of erlan is always between .^■0 anil 3-1. — Breil/it/iipl. 



B. Before 



