Monthly microscopical journal: transactions of the Royal Microscopical Society, and record of histological research at home and abroad . X 360 F^,F^j£Uy dfJ* WJ^esi>kCo. sc^. S-brixo-tur es iti. Qtsidxajn Leacibe. ..sv5:^.v; ^. je. : tp u o t-ur e m P e p 1:1 -r Structures in Ohsldian, Ferlite, and Leucite. By F. Butleij. Ill sections similar to those which an octahedron would yield (Fig. 8).They are often feebly translucent towards their margins. Thisprobably results from peroxidation of the protoxide of iron whichthe mineral, if magnetite, would contain. I believe tha
Monthly microscopical journal: transactions of the Royal Microscopical Society, and record of histological research at home and abroad . X 360 F^,F^j£Uy dfJ* WJ^esi>kCo. sc^. S-brixo-tur es iti. Qtsidxajn Leacibe. ..sv5:^.v; ^. je. : tp u o t-ur e m P e p 1:1 -r Structures in Ohsldian, Ferlite, and Leucite. By F. Butleij. Ill sections similar to those which an octahedron would yield (Fig. 8).They are often feebly translucent towards their margins. Thisprobably results from peroxidation of the protoxide of iron whichthe mineral, if magnetite, would contain. I believe that thesecrystals are magnetite altered at their margins into limoniteor possibly in some cases hematite. Lasaulx has noted the occur-rence, in the altered lavas of Auvergne, of microscopic pseudomorphsof hydrated oxide of iron after magnetite, in distinct octahedra ofa brownish-red colour and translucent.* I merely record this pointbecause, from the slight marginal translucency of these crystals,some doubt might be experienced as to whether or not theyreally represent magnetite. The hand specimen, from which thesection was cut, attracts the magnetic needle, and seems, at certainspots, to repel it also to a very slight extent. Fig.
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Keywords: ., bookcentury1800, bookdecade1860, bookpubli, booksubjectmicroscopy
