ITALIAN PETROLOGICAL SKETCHES 37 1 



NOTES TO TABLE V. 



1. Leucitite, Capo di Bove, Bunsen anal. 



2. Leucitite, Crocicchie, Bracciano, Washington anal. 



3. Leucitite, Sassi Lanciati, Bolsena, mean o£ 2, Ricciardi. 



4. Leucite-basanite, Toscanella, Bolsena, Ricciardi. 



5. Leucite lavas, Vesuvius, mean of 49 anals.. Roth, Geologic, 11,268. 



6. Leucite-tephrite, Rocca Monfina, Rohrig. 



7. Leucite-tephrite, Bracciano, Washington. 



8. Leucite-tephrite, Monte Cavallo, Bolsena, Washington.' 



9. Leucite-tephrite, Monte Bisenzio, Bolsena, Ricciardi. 

 ID. Leucite-tephrite, Montalto, Bolsena, Ricciardi. 



11. Leucite-phonolite, Lake Bracciano, Washington. 



12. Leucite-phonolite, Bagnorea, Bolsena, Washington.' 



13. Leucite-phonolite (?) Bolsena, Vom Rath. 



14. Leucite-trach3-te. San Rocco, Mte. Vico, Washington.' 



15. Leucite-trachyte, Monte Venere, Viterbo, Washington. 



16. Leucite-trachyte, Madonna di Lauro, Viterbo, Rohrig. 



17. Leucite-trachyte (?), Monte. S. Antonio, R. Monfina vom Rath. 



18. Leucite-trachyte, Viterbo, vom Rath. 



the most representative being selected. Many more must be 

 made before these rocks can be adequately treated from a chem- 

 ical standpoint. 



By far the best defined type is that of the so-called lencidtes, 

 which are quite constant in structure and mineralogical com- 

 position, as already described. The chemical composition of 

 typical leucitites is given in Table V, Nos. i, 2, and 3. They 

 are very basic rocks, with high iron and lime, quite high 

 magnesia, and high alkalies. Lezicitc-basalts seem to be quite 

 unknown in the Italian localities — perhaps owing to the rich- 

 ness of the magma in lime, which makes a basic plagioclase- 

 free rock almost an impossibility if any of the MgO is withdrawn 

 from a possible diopside molecule to form olivine. Outside of 

 the Vesuvian region, where they occur in abundance, lejicite- 

 basa?iites are only met with in small amounts. Their analyses 

 (Nos. 4 and 5) resemble those of the leucitites except that they 

 are higher in magnesia and iron as well as in lime, and those of 

 Bolsena low in alumina. The leiicite-teplirites form a group which 

 is one of the most difficult to classify satisfactorily owing to the 



' Made since publication of their respective papers. 



