92 ACCOUNT OF A MINEBAL FltOM ORKNEY. 



A question may here arise, whether these ingredients are 

 chemically combined, or only in a state of mechanical admix- 

 ture in the mineral ? The homogeneous appearance, and 

 crystalline texture of this substance, and the nearly uniform 

 proportions of the ingredients obtained from it, by different 

 experiments, would lead to the conclusion that the mineral in 

 question is a chemical compound. These, however, may be 

 the result of an intimate mechanical mixture of the earthy 

 salts of which it is composed. 



The iron appears to be united by affinity to the sulphate of 

 barytes, as it is not separated in any considerable degree du- 

 ring the solution of the carbonates in diluted muriatic and ni- 

 trie acids ; but requires for its separation from the sulphate of 

 barytes, digestion in one of those acids, after the separation of 

 the more soluble ingredients. 



The existence of carbonate of lime in this mineral is en- 

 teresting. In this particular it accords with what has been ob- 

 served by ScHMEissER, Thomson, and Stromeyer, in native 

 carbonate of Strontia. It is remarkable, that the portion of 

 carbonate of lime in the Orkney mineral, is not very different 

 from the quantity of carbonate of sti-ontia in Arragonite ; a cir- 

 cumstance which renders it probable, that the carbonate of 

 lime is in a state of chemical union with the carbonate of 

 strontia. 



Should this substance be regarded as a variety of Strontia- 

 nite, or as a distinct mineral species ? If the latter conjecture 

 be entertained, it will be necessary to give it a name ; which 

 may be derived, either from its composition, as Bary-Stron- 

 TiANiTE, or from its locality, as Stromnite. 



IV. 



