304 J. F. Kemp — Basic Dike near Hamburg, JV. J. 



I. Analysis of spheroids from the Hamburg dike by Prof. L. M. 

 Dermis of Cornell University. 



II. Recalculation of I, 3,886* per cent CaC0 3 having been taken 

 out. 



III. By E. Hussak of " leucite-pseudo-crystals " from Brazilian 

 Foyaite, 'iSTeues Jahrbuch, 1892, II, 146. 



IV. By J. F. Williams, " pseudo-leucites " from leucite-syenile 

 dike rock. Magnet Cove Ark. Ann. Rep. Dir. Geol. Surv. Ark., 

 1890, II, p. 270. 



V. By Rammelsberg. Analcite from the Cyclopean Islands. 

 Min. Chem., 804, quoted by Dana. 



VI. By Nikolayev of massive analcite from Blagodatsk, Russ. 

 Berg. Jahrb., II, 376, 1881. Zeitschr. Kryst., xi, 392, 1886. 

 Dana's Mineralogy, new ed., 597. 



VH. By Rammelsberg, Leucite of Vesuvius. Fogg. Annalen, 

 xcviii, 142. 



VIII. By Smith and Brush, Elaeolite from Magnet Cove, Ark. 

 This Journal, II, xvi, 371. 



A comparison of II and V shows at once that the spheroids 

 are practically analcite, for while the lime and alumina are 

 high, and the silica rather low, the correspondence is extremely 

 close, when it is remembered, that some little plagioclase is 

 confessedly present, and a few other small impurities. The 

 parallel between the soda and potash, and those of the massive 

 analcite, Analysis VI, is very close. In respect to a change 

 from leucite, we have to account for an immense accession. of 

 soda, and as regards the corresponding alteration from nephe- 

 line, a much smaller accession of potash. But the analysis of 

 elseolite from Magnet Cove gave the alkalies in about the same 

 ratio. In either change outlined above the alkalies have de- 

 creased in amount more than is compensated by the increase 

 in water. On the whole, other things being equal, the analysis 

 rather favors original nepheline, than original leucite. 



Analcite as an alteration product is well known from both 

 nepheline and leucite. Abundant literature on both changes 

 is cited by Rosenbusch, and hardly needs repetition. It is 

 especially interesting to mention the occurrence of this min- 

 eral in the teschenites, in which it is generally regarded as sec- 

 ondary after nepheline. The possibility of both these changes 

 may be taken for granted. 



On the one hand in the feldspathic rocks (minettes of Ger- 

 many and in the mica-diabase or kersantite from Franklin 

 Furnace), what appear to be essentially the same structural phe- 

 nomena as the spheroids, occur with feldspar centers and 

 biotite rims. No one has thought of leucite in these connec- 

 tions, nor does there seem any reason to do so. A group of 

 feldspar crystals, irregularly aggregated have formed, and have 

 attracted to their common border a tangential rim of biotite. 



