Aspects of Kentish Local History

refractive index is less than that of Canada Balsam. It is frequently spherulitic. No quartz was seen in the slide. Biotite is both porphyritic and scattered through the groundmass, and sometimes shows alteration to chlorite, and to magnetite. Accessory zircon occurs.
   7. PALE BROWN GRIT, the hand specimen showing distinct yellowish coating of some of the grains. The slice shows that almost all the grains are of quartz, and two distinct grain-sizes occur, a few of these being up to about 5 mm., but the majority measure only 0·2 to 0·5 mm. Sericitic mica has grown between the grains, and there are rare small detrital crystals of zircon.
   8. VEINED CHLORITIC SCHIST. A fine-grained bluish-green rock in the hand specimen. Seen under the microscope to consist of rather angular quartz grains, averaging 0·1 to 0·2 mm. in size, and showing strain-extinction. These grains are packed round by abundant chlorite, with a few muscovite flakes. A conspicuous vein consists of quartz and calcite, and accessory zircon is present both in the schist and in the vein. No felspars were seen in this rock.
   9. APLITE. Fine-grained speckled rock which consists of allotriomorphic crystals of quartz, orthoclase and oligoclase. These three minerals are present in approximately equal proportions, and are also equal in grain size, about 0·3 mm. The rock also contains a little muscovite and zircon, and is stained by limonite.

   10. BASIC DIORITE, or possibly CAMPTONITE. Dark medium-grained, rather weathered rock, made up almost entirely of zoned feldspars and hornblende in aproximately equal quantities. The saussuritization of the basic centres of the feldspars has gone too far for them to be identified, but the fresh rims suggest oligoclase. The hornblende shows green, brown and yellow pleochroism. Ilmenite and apatite also occur.
   11. MUSCOVITE-BIOTITE GRANITE, fine-grained. The slice shows that quartz is abundant, and the chief felspar is orthoclase, with less common oligoclase and rare microcline. Both muscovite and biotite are common, and zircon and apatite are accessory. The grains are allotriomorphic, the quartz showing sutured margins, and the size of grain is about 1 mm. maximum.
   12. QUARTZITE, with white spots and partly stained red. Made up of coarse quartz grains, mostly from 0·5 to 3 mm. in size, some coated with a mineral resembling muscovite. This coating may account for the white spots visible in the hand specimen. Limonite and haematite are both present. The rock appears to have been slightly sheared and brecciated.
  13. ? BIOTITE-APLITE. A very weathered pink rock consisting mostly of quartz and kaolinized felspar, some of which may have been oligoclase. Very altered biotite is subordinate to the other minerals.