48 EMERY xMINE OP CHESTER, MASS. 



and then goes on to state, " from which it would appear that 

 protoxide of iron is an essential chemical ingredient in emery, 

 and not an accidental admixture.* Dr. J. Lawrence Smith's 

 experiments lead to the same result, but be considers the oxide 

 of iron to be an irregular mixture with the alumina and not a 

 regular chemical constituent. In either case I think emery 

 ought to rank as a separate species, and not as a granular 

 variety of corundum, from which it differs so in physical 

 characters." 



I would here remark that Dr. Jackson's conclusion would 

 be correct in the first state of the case, were the iron an essen- 

 tial chemical ingredient ; but in the latter it would be erroneous, 

 and introduce inextricable confusion into the science of min- 

 eralogy by admitting mere mechanical mixture as a specific 

 distinction. 



Prof. C. TJ. Shepard, writing on the same point, says: "His 

 conclusions (Dr. Jackson's) would obviously be acquiesced in 

 were it not for the strong resemblance in striae and cleavage 

 between the emery and common corundum, making it impos- 

 sible for us to separate the substances crystallographically 

 from one another. Nothing like a perfect crystal of emery has 

 yet been found at the mine ; but it is quite remarkable that the 

 mineral is here generally coarsely massive, or in large separate 

 individuals often of the size of kernels of Indian corn, whose 

 cleavages are perfect, and which present on their planes the 

 delicate striae so characteristic of corundum from the Carnatic." 

 Yet Prof. Shepard is for making emery a new mineral species 

 and calling it Emerite, with the formula Fe Si. 



If the views of Profs. Jackson and Shepard are to be taken 

 as correct, the question as to the mineralogical position of 

 emery is easily settled without resorting to any new mineral 

 species. It is simply a massive iron-spinel (hercynite) with 

 the anomaly of having a hardness equal to corundum. 



IRON-SPINEL. EMERIES. 



Jackson. Shepard. 



Alumina 58.75 60.49 -> -v-, -™ 



Protoxide iron 41.25 39.60 J 



I would say at this point that if the mineral of Chester is to 



* An examination of my analyses in 1850, which it is supposed are the 

 ones referred to here, most certainly do not sustain the conclusion. — J. L. S. 



