-±04 W. H. Ilobbs — Lime- and- Alumina-bearing Tale. 



of the precipitate to fall coarsely crystalline under the con- 

 ditions. In certain special cases in which certain substances 

 mentioned, which would otherwise exert solvent action, are 

 present the precipitation is made complete. The contaminat- 

 ing- effect of such substances when complete precipitation is 

 induced may be corrected by dissolving the precipitate in sul- 

 phuric acid and recrystallizing by evaporation. 



Art. XLIX. — On a Rose-colored Lime- and- Alumina-bearing 

 Variety of Talc ; by Wm. H. Hobbs, Madison, Wis. 



The crystalline dolomite of the vicinity of Canaan, Conn., 

 is well known as a locality for white pyroxene and white and 

 pale green tremolite. Some of this tremolite has recently been 

 shown to be pseudotnorphic to the white pyroxene.* Small 

 amounts of quartz and colorless mica, and isolated crystals of 

 pyrite, are present in the rock at many localities, and veins of 

 calcite are occasionally met. Except near the boundaries of 

 the horizon, where the rock passes by gradations toward a 

 gneiss or schist, these are the only common minerals. Phlogo- 

 pite I have found in clear brown scales a millimeter or more 

 in diameter on the road running south from Rattlesnake Hill. 

 The numerous openings which are made in the dolomite for 

 supplying the lime-kilns of the vicinity, furnish opportunities 

 for the discovery of any less common constituents that may be 

 included in the rock. Mr. J. S. Adam, former analyst of the 

 Barnum and Richardson Company of Lime Rock, has in his 

 mineral collection at Canaan, several minerals of this character 

 which have not been carefully studied. I am under obliga- 

 tions to him for the material which is here described. It was 

 met with in the Adam Quarry which is located a mile south- 

 east of the village of Canaan. The specimens given me are 

 enclosed in the white crystalline dolomite whose grains average 

 two millimeters in diameter.f Scattered through the dolomite 



* Wm. H. Hobbs, Notes on some Pseudomorphs from the Taconic Region, Am. 

 Geol., x, 44 (1892). 



f I am permitted by Mr. Adam to publish analyses by him of the dolomite of 

 the vicinity, which show it to contain calcium and magnesium carbonates in the 

 proportions of normal dolomite : 



Canaan Lime Company's Quarry. Calculated for 

 Granular. Cleavage Pieces. CaC0 3 . MgC0 3 . 



CaC0 3 52-62 5440 54-35 



MgCOs 46-25 4512 45-65 



AI0O3 \ 



Insoluble residue ... 0-17 0-08 



Fe.O, , 24 . 25 



99 28 99-85 100-00 



