V.—On the Origin of Certain Pegmatite Veins

Extract

During a visit to the South of Sweden in the Summer of 1902 I noticed the frequent occurrence in granite of pegmatite veins showing a succession of small but very regular foldings, which, however, did not affect the parent rock. In sett quarries where these folded veins existed the rift of the rock was perfectly regular on each side of the pegmatite, proving conclusively to my mind that the contortion of the veins took place prior to the consolidation of the main mass. The granite of this district occupies a wide area, and possesses a very uniform mineralogical constitution, although it varies much in texture between a rather coarse-grained granitite and a fine-grained, compact, gneissose rock possessing well-marked foliation. The pegmatite veins are fairly numerous, but are generally rather insignificant in width, occasionally thinning out to mere streaks not more than a few inches in thickness.