224 Field Columbian Museum — Geology, Vol. i. 



4 H 2 0, 6 (Mn, Ca) O, 6 Si 2 , or H 2 (Mn, Ca) 6 Si 6 19 + 3H 2 O. Cora- 

 paring the percentages called for by the formula, with the writer's 

 analysis calculated to ioo% (reckoning Fe O as Mn O), the results are 

 as follows : 



Analysis Calculated 

 Theory. to ioo. 



6 Si O s 42.91 44.76 



|(6MnO) 40.51 38.86 



J(6CaO) 8.00 8.21 



4H,0 8.58 8.17 



100. 100. 



Here the greatest discrepancy to be noted is in the percentage 

 of Si 2 , which is noticeably higher in the analysis than the theory 

 calls for. Mn O is also a little lower. Yet it is believed that this 

 formula better agrees in general with analyses of the mineral and bet- 

 ter expresses its constitution than any hitherto proposed. Flink's 

 formula, 2 (Mn, Ca) Si 3 -f- H 2 O, reckons all the water as water of 

 crystallization, which is clearly incorrect. Moreover, the percent- 

 age of Mn O called for by his formula, 41.4%, is larger than has 

 ever been obtained. Barwald's formula, R (ROH) 2 Si 3 8 + ac l-> 

 gives percentages nearly like that proposed by the writer, but the 

 compound represented by such a formula would less resemble other 

 zeolites in manner. of constitution than does that of the writer's 

 formula. Moreover, one would expect a darker color if the molecule 

 Mn OH were present in the mineral. 



CALEDON1TE. 



STEVENSON-BENNETT MINE, ORGAN MTS., NEAR LAS CRUCES, NEW MEXICO. 



MUSEUM No. M 5486. 



A single specimen of this mineral was picked up by the writer 

 on the dump of the Stevenson-Bennett mine in the spring of 1896. 

 It is the only specimen ever found there, so far as I am aware. It 

 is also the second or possibly the third occurrence of the mineral 

 reported in America. It is known to occur* at the Cerro Gordo 

 mines in California, and has been reported from Mine la Motte, 

 Missouri, but the report needs confirmation. In the specimen 

 secured by the writer the mineral is in the form of several distinct 



♦Dana's Mineralogy, p. 925. 



