892 



SCIENCE 



[N. S. Vol. XXVII. No. 701 



Mr. D. B. Sterrett described the discovery 

 of meerschaum in New Mexico, which is of 

 interest since the world's supply, coming 

 chiefly from Asia Minor, scarcely meets the 

 demand. A chemical analysis, by Mr. George 

 Steiger, of material from the Dorsey claim, 

 twelve miles northwest of Silver City, corre- 

 sponds very closely with the composition re- 

 quired by the formula generally given for 

 meerschaum, that is, 2H,0 + 2MgO -f 3SiO,. 

 The mineral occurs in fissures, joints and 

 seams in a magnesian limestone formation, 

 probably of Ordovician age. Two varieties 

 were observed, massive and nodular meer- 

 schaum. Only surface material was available 

 for examination. This possessed many of the 

 properties of ordinary meerschaum, including 

 the important one of absorbing a mixture of 

 wax and nicotine. On the other hand, the 

 majority of the specimens examined were 

 heavier than meerschaum ordinarily used for 

 carving, and some of them contained tufts of 

 fibrous material which made it difficult to 

 work and polish. 



Regular Program 

 The Intrusive Rocks of ML Bohemia, Mich- 

 igan: Mr. Fred. Eugene Wright. 

 Mt. Bohemia is located near the end of 

 Keweenaw Point, Michigan, and consists in 

 large part of lava flows and interbedded con- 

 glomerates of the Keweenaw formation. On 

 its south flank a peculiar intrusive rock mass 

 is exposed which is unique in character and 

 has long attracted the attention of geologists. 

 Two rock types occur within this intrusive 

 body — a dark, granitoid rock consisting chiefly 

 of red,, idiomorphic oligoclase (AbjAUj), pyr- 

 oxene and magnetite in such proportions that 

 chemically the rock is practically identical 

 with the Keweenaw ophites. This rock was 

 originally called orthoclase gahbro by Irving 

 in his monograph on the copper-bearing rocks 

 of the Lake Superior region, but the name 

 oligoclase gabhro seems preferable in view of 

 the fact that practically no free orthoclase is 

 present in the rock. The second rock type is 

 entirely surrounded by the first, and is brick 

 red in color; qualitatively it consists of min- 

 erals identical with those of the enclosing 



oligoclase gabbro, its essential constituents 

 being quartz and red idiomorphic oligoclase 

 with subordinate amounts of the colored con- 

 stituents. The alteration of the different con- 

 stituents in the two rock types is character- 

 istic and in every way similar, and substan- 

 tiates the inference that they are genetically 

 closely related, and that the red rock is an 

 aplitic phase of the oligoclase gabbro. It may, 

 therefore, be termed gahbro aplite. The posi- 

 tion of the two rocks in the quantitative classi- 

 fication of Cross, Iddings, Pirsson and Wash- 

 ington is : for the oligoclase gabbro. Class III., 

 Order 5, Rang 4, Subrang 3; in short, Bo- 

 hemial Auvergnose; for the gabbro aplite. 

 Class II., Order 4, Rang 3, Subrang 4 {Bo- 

 hemial Tonalose). The geologic relations of 

 the two rocks were discussed in detail with a 

 view to a possible eutectic relation of the con- 

 stitutents in the aplite which would then be 

 the last to crystallize, and by a process of frac- 

 tional crystallization be forced toward the 

 center. By actual experiment, however, it 

 was found that, on heating powder of both 

 rocks in an electric resistance furnace for one 

 hour at 1,132° C, the aplite had just begun 

 to melt, while the oligoclase gabbro had only 

 sintered slightly; while at 1,150°, under the 

 same conditions, both the gabbro aplite and 

 the oligoclase gabbro showed signs of fusion. 

 (These temperature measurements were made 

 by Dr. W. P. White, of the Geophysical Labo- 

 ratory. His courtesy is herewith gratefully 

 acknowledged.) This temperature range is so 

 slight that the idea of eutectic relations in the 

 dry melt is at least not strongly substantiated 

 by experiment. The objections to any infer- 

 ence which might be drawn from the behavior 

 of rocks of this type in the dry state were 

 pointed out and the means for attacking such 

 problems briefly indicated. The contact rela- 

 tions of the aplite to the oligoclase gabbro 

 (change in granularity, etc.) were also briefly 

 considered, together with the contact meta- 

 morphism of the adjacent ophites by the in- 

 trusive oligoclase gabbro. 



Some Structural Details in the Pittsburg 

 Region: Mr. G. 0. Martin. (No abstract 

 furnished.) 



