On some pseudomorphs after a lime-soda felspar

Abstract

Two or three years ago Mr John Smith of Kilwinning was kind enough to send me some specimens of a very interesting pseudomorph, which I understand him to say occurred at Dreghorn, in Ayrshire. He sent through me, at the same time, some other specimens for presentation to the Collections, of Scottish Mineralogy, which have been under my charge for the last thirteen years or more. After carefully examining the whole of specimens Mr Smith sent, with a view to discovering what mineral had been replaced, I came to the conclusion that they were twins on the Albite Law, of an anorthic mineral, which I thought might be either Labradorite or Bytonite—more probably the former. It was evident that they had been weathered out of some hemi-crystalline eruptive rock in which they had occurred as phenocrysts. Accordingly, the donation was reported in due form to Sir Murdoch Smith the Director of the Museum at that time, as pseudomorphs after an anorthic felspar, and as such they were placed on exhibition. Sir Murdoch Smith eventually published the List of Donations to the Scottish Mineral Collection in the Annual Eeport, as had always been done while he was Director. The specimens in question were exhibited in their proper place amongst the pseudomorphs, and but for their perfect crystalline development I might hardly have given them another thought. Shortly after the Report was published however, I learned that Mr Smith had given several sets of these to other workers and that an independent