THE 



PHILOSOPHICAL MAGAZINE 

 AND JOURNAL. 



3P^ OCTOBER 1823. 



XLIX. Complete Descriptmi of Erlan, a Mineral long inis- 

 ujiderstood, and nevuly determined. By Augustus Breit- 

 HAUPT, and C. G. Gmelin*. 



I. Determination of Erlan as a Minei-al Species. By Aug. 

 Breithaupt, of Freibei'g, Inspector of Precious Stones. 



A. Characteristic. 



Erlan. — T^HTS mineral varies in lustre from glistening to 

 -*■ dull ; in the streak it has a resinous lustre : its 

 colour is greenish-gray, usually light, the streak is white. It 

 occurs massive ; and in small and fine-granular distinct con- 

 cretions, from which it passes to compact. Its fracture varies 

 from foliated to splintery and even. Hardness from 6'25 to 

 7.f Specific gravity from 3*0 to 3'1. 



B. Observations respecting the History and Discovery of Erlan. 



I first saw this mineral in the autumn of 1818, lying as a 

 flux at the smelting-furnace (HUttenhose) of the Erla Iron- 

 Works (commonly called Erlhammer) near Schwarzenberg, 

 in the Saxon Erzgebirge ; I was then convinced that it was 

 not limestone, for it was much too angular, too hard, and too 

 heavy. It has been made use of as a flux in these extensive 

 iron-works for above two centuries, as well as in some neigh- 

 boui'ing works ; but although they have often been visited by 

 mineralogists and chemists, yet no one ever doubted but that it 

 was lunestone. I immediately sought for the place where it was 

 found, and ascertained that erlan mixed with mica constituted 

 part of the oldest gneiss-formation. In one place there were also 



•Abstracted from Scliwcigger and Meincclce s Neues Journal fur Chemie tend 

 Phi/sik, N. li. band 7, j?^ 7(>, where it is given as an extract from Breitiiaupt's 

 Complete Characteristic of the Mineral Kingdom, a work nearly ready for 

 publication when the extract appeared, which was in February last : the 

 kditors inform us that this work may be considered as a supplement to 

 Hoffmann and Breithauj)t's Manual of Mineralogy. 



\ That is, it varies from being somewhat harder than apatite, to the 

 hardness of sodalitc or actynolite. 



Vol. 62. No. 306. Oct. 1823. H h strata 



