24 A.M. Finlayson—Ore-bearing Pegmatites of Carrock Feil. 
two types—segregation pegmatites and intrusive pegmatites. The 
view that pegmatites grade into normal quartz-veins has been main- 
tained in different districts by various writers, as, for instance, 
Crosby & Fuller,’ J. F. Kemp,’ A. H. Brooks,*® Joseph Barrell,‘ and 
A.C. Spencer.? R. Beck concludes that pegmatites are products of 
crystallization from superheated waters, which remained, after the 
separation of the chief constituents of the magma, as a concentrated 
solution containing the rarer metallic elements. He is thus in 
agreement with Brogger, Arrhenius, Vogt, and Grubenmann, all 
of whom support the intimate relation between pegmatites and ore- 
veins. Hastings expresses similar views with respect to the pegmatites 
of the Eastern United States,’ which he regards as true dykes, 
except where excess of water and of .mineralizers have produced, 
first, pneumatolytic tin- and apatite-veins, and finally veins con- 
taining gold, silver, or galena. 
The most pronounced advocate of the connexion between pegmatites 
and normal quartz-veins, however, is J. E. Spurr, who has advanced 
a theory of progressive derivation of gold-quartz veins from granitic 
magmas by siliceous magmatic differentiation.’ While this hypothesis 
may be locally applicable, there are, in many districts, difficulties in 
the way of its acceptance, owing to the absence of transitions from one 
vein-type to another. To take a single instance known to the writer, 
the gold-quartz veins of the west coast of New Zealand,° while related 
to the tectonic movements and granitic intrusions of the Alpine region, 
show no relation whatever with the abundant pegmatites and barren 
quartz-veins of the granites themselves. Again, in the Grainsgill 
district under consideration we have, on the one hand, ore-bearing 
pegmatites representing the super-acid phase of segregation and 
differentiation of the magma; and, on the other hand, lead-quartz 
veins in fissures, showing no (structural) similarity to the pegmatites. 
They have clearly been deposited from circulating waters at a later 
date. The occurrence in the lead-veins, however, of the minerals 
stolzite and wulfenite, serves to link the two types together to 
a certain extent, and to indicate that the ores have probably been 
derived from a common source. 
Geological Occurrence of Tungsten-ores.—The range of occurrence of 
tungsten-ores is very remarkable, and gives important evidence on 
the question of relations between the different vein-types. The facts 
of occurrence, with examples, are given below :— 
1. Pyrogenetic Minerals.—Tungsten-ores occur as original pyrogenetic 
compounds in granitic and allied rocks, chiefly as small percentages of 
tungstic oxide, often with tin oxide and molybdic oxide, in tantalates 
' Technology Quarterly, 1896, ix, p. 326. 
2 Bull. Geol. Soc. Amer., 1898, x, p. 361. 
3 20th Ann. Rep. U.S. Geol. Surv., 1898-9, pt. vii, p. 425. 
4 22nd Ann. Rep. U.S. Geol. Surv., 1900-1, p. 511. 
> Prof. Paper No. 25, U.S. Geol. Surv., 1904, p. 41. 
6 Rep. Brit. Ass., Trans. of Sections, 1905, p. 400. 
* Amer. Inst. Min. Eng., 1908, Bull. xxi, p. 319. 
* Prof. Paper No. 5d, U.S. Geol. Surv., 1905, p. 129, and Economic Geology, ii, 
No. 8, p. 781. 
9 A. M. Finlayson, Trans. N.Z. Inst., 1908, xli, p. 85. 
