. Bulletin of the British Museum (Natural History), Mineralogy. 152 PETROLOGICAL STUDIES IN GLEN URQUHART, INVERNESS-SHIRE of the garnet is 1-786 (sodium light: ± 0-003), a- shghtly lower value than the average for kyanite schist garnets in Glen Urquhart (1-796). Garnets in Group III are deep- red, xenoblastic and reach 6 cm. in diameter. Of the remaining accessory minerals pyrite and apatite occur in Groups I and II, rutile in Groups I and III (abundantly and in large crystals in the latter), graphite in Group II, and serpentine in Group III. Petrology Group I: Epidosites, epidote-hornblende
. Bulletin of the British Museum (Natural History), Mineralogy. 152 PETROLOGICAL STUDIES IN GLEN URQUHART, INVERNESS-SHIRE of the garnet is 1-786 (sodium light: ± 0-003), a- shghtly lower value than the average for kyanite schist garnets in Glen Urquhart (1-796). Garnets in Group III are deep- red, xenoblastic and reach 6 cm. in diameter. Of the remaining accessory minerals pyrite and apatite occur in Groups I and II, rutile in Groups I and III (abundantly and in large crystals in the latter), graphite in Group II, and serpentine in Group III. Petrology Group I: Epidosites, epidote-hornblende skarns and plagioclase skarns. The parageneses observed in this Group are set down in Table XI. The great variability of the Group is evident. There are seldom more than two representatives of a paragenesis amongst the slides examined. The appearance and nature of the epidosites and epidote-hornblende skarns has been sufficiently covered in preceding pages and it remains to describe in greater detail the plagioclase skarns and transi- tions between them and the first two types. These rocks, of insignificant areal extent, are found close to the serpentinite margin. The host rock is always kyanite schist, and early stages of transformation are always marked by the crystalloblastic growth of large plagioclases (Text-fig. 9). At a later stage the whole rock may be composed of plagioclase (oligoclase). It is always poorly crystallized, showing patchy extinction, ragged intergrowth, irregular boundaries and other signs of replacement. 1^7^:^. 2. ctn Fig. 9. Polished face of a hand specimen of mica schist showing oligoclase porphyro- blasts that have grown into a distinct mineral zone and have thrust themselves out into the groundmass of the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museu
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