238 Washington — Catalan Volcanoes and their Rocks. 



form were the rock holocrystalline. The}* are thus contrasted 

 with the otherwise mineralogically similar vitreous and feld- 

 spar-free basalts proper, to which the older name " magma- 

 basalt " is more truly applicable, though of doubtful form and 

 etymology. These are less markedly deficient in silica, or even 

 with a slight excess of this, and at the same time not as strik- 

 ingly alkalic in character as the rocks mentioned above, so that 

 lenads would not be necessarily present, and if so only in very 

 small amount, were the rock holocrystalline, but there may be 

 considerable olivine if there is a deficiency in silica. 



These magmatic differences between the limburgites and the 

 augitites on the one hand, and the feldspar-free vitreous basalts 

 on the other, which are only vaguely recognized in the pre- 

 vailing classifications, are clearly brought out in the quantita- 

 tive classification. In this the typical examples of limburgites 

 and augitites, so far as they are represented by good analyses, 

 fall in the lenic orders of salfemane, especially in portugare, 

 and' the greater part of them in the alkalicalcic rang limbur- 

 gase and the dosodic subrang Jimburgose : while (it may be 

 added), the most typical monchiquites, in which a highly sodic 

 and an analcitic base is abundant, fall in the same order, but in 

 the domalkalic rang monchiquase and the dosodic subrang 

 monchiquose. On the other hand, the basalts proper belong- 

 almost exclusively to perfelic orders, germanare and gallare, 

 and to docalcic rangs and presoclic subrangs of these, notably 

 hessose and auvergnose.* 



Occurrence. — Clearly recognizable specimens of this type 

 were obtained by me only at one locality, the massive flow at 

 the Fuente de San Roque, about one kilometer west of Olot, 

 on the south bank of the Fluvia River. Other specimens 

 which much resemble this, but which contain traces of feld- 

 spar and are therefore transitional toward the former type, 

 were obtained near a small wine-shop above the chapel of Sant 

 Medir, at Llora, and at the dike 3 kilometers from Olot, on the 

 road to Santa Pau, already mentioned. 



General Characters of the District. 

 Mineralogical characters. — These are so simple and are so 

 evident from the descriptions which have been given above, 

 that little need be said of them here. Augite, olivine and 

 titaniferous magnetite are invariably present, the first always 

 in very notable amount, and the last two in much smaller 

 quantities. Hornblende, biotite, and titanite (which last 

 might be expected in view of the richness of the rocks in tita- 

 nium), are entirely absent, not a single grain of either of these 

 having been observed by me in any of the sections. 



*Cf. ladings, Prof. Paper XL S. Geol. Surv.. No. 18, pp. 90, 91, 1903; 

 and Washington, Prof. Paper U. S. Geol. Surv., No. 14, pp. 75, 76, 80, 1903. 



