No. 2395. LUDWIGITES FROM IDAHO AND KOREA— SHANNON. 



669 



Since several of the constituents which are present in minor 

 amounts are obviously present as impurities, it is difficult to decide 

 which of these should be included as essential to the ludwigite. The 

 copper and sulphur are certainly extraneous, a part of the former and 

 all of the latter being present as bornite. The presence of the bornite 

 introduces some error into the analysis, as it itself contains ferrous 

 iron, and the hydrogen sulphide formed by the action of hydrochloric 

 acid upon it would naturally reduce some ferric iron to the ferrous 

 state. The copper in excess of bornite is probably present as thin 

 staining films of chrysocolla or malachite. These impurities are, 

 however, present in too minor amounts to affect the broader ratios 

 of the ludwigite. The constituents which are probably essential to 

 the mineral yield the following ratios: 



Ratios of Ludwigite from Lemhi County, Idaho. 



The general formula derived from these ratios is, then — 



4(Mg, Fe)0. Fe 2 3 - B 2 3 - 



Following Schaller this composition may be interpreted as an iso- 

 morphous mixture of magnesioludwigite and ferroludwigite in the 

 molecular proportions of approximately 7 parts of the former to 3 

 of the latter; or the material is, by weight, 68 per cent magnesio- 

 ludwigite and 32 per cent ferroludwigite. The essential constituents 

 given above are below recalculated to 100 per cent and compared 

 with the percentages calculated for a mixture of this composition. 



The material is thus higher in the magnesioludwigite molecule 

 than any ludwigite yet analyzed except the end member itself. 



LUDWIGITE FROM KOREA. 



Introduction. — The United States National Museum has received 

 from Mr. J. Morgan Clements several specimens labeled ilvaite from 

 Heoth 1 Kol Mine, Korea. (Cat. No. 93729 U.S.N.M.) Since the 



