Janus Pannonius Múzeum Évkönyve 43 (1998)( Pécs, 1999)

Régészet - Schléder, Zsolt–T. Biró, Katalin. Petroarchaeological studies on polished stone artifacts from Baranya county, Hungary

SCHLÉDER, ZS. & К. T. BIRÓ: PETROARCHEOLOGICAL STUDIES ON POLISHED STONE ARTIFACTS FROM BARANYA COUNTRY 79 growth. Composition is augitic (based on a 40° Y/C extinction angle). The extinction is undulatory. It rarely contains opaque mineral inclusions. Pyroxene sometimes turns into clay mineral. Idiomorphic plagioclases occur either as 1-1.5 mm porphyries or as 0.25 mm large grains. Both types of plagioclase tend to turn into calcite, chlorite, seriate. On the edge of smaller, weathered grains unaltered plagioclase can be seen as a result of syntaxial overgrowth. The opaque mineral is determined as ilmenite, based on its habit. They are about 0.125 mm large. Small, idiom orphie apatite fibres occur as inclusion in plagioclase and glass. Space among the plagioclase laths is filled with rock-glass which always turns into pleochroic chlorite (Photo Plate V/3). Sedimentary rocks Limestone Sample nr. 1 was described as limestone. Macroscopic features. Homogeneous, fine-grained, black coloured rock, sometimes with 1 mm thick calcite veins. Microscopic features. Name of rock: crystalline limestone, originally mudstone (Dunham), extraclastic biosparit (Folk). It consists of 50-80 urn large, nearly isometric, closely packed sparite crystals. Contains 0.125 mm large well-sorted quartz grains, filaments of muscovite (all together 4-5 %), lots of dendritic opaque minerals (organic matter) and a few Ostracodes. Local enrichment (30-40%) of clastic particles is probably caused by bioturbation. The rock includes a 1-2 mm thick calcific vein as well. Frequently, cubic zeolites occur in the calcite veins (Photo Plate VIII). Metamorphic rocks Serpentinite Tool nr. 5. was classified as serpentinite. Macroscopic features. Fine-grained rock. Its colour changes from place to place: light green colour bands and mottles alternating with violescent dark green mottles. Microscopic features. Name of rock: serpentinite. Texture: fibroblastic. The rock consists of serpentine (chrysotile and antigorite), talc and secondary opaque minerals. The opaque mineral is supposed to be magnetite. Orientation of chrysotile and opaque mineral refers to the size and position of original minerals (1-1.5 mm large pseudomorphs after olivine and orthopyroxene). Talc sometimes occur as long veins. Secondary limonite can often be found next to the opaque minerals (Photo Plate VI 12). Metadolerite Sample nr. 6 was described as metadolerite. Macroscopic features. Poppy-seed texture rock with 2 mm large, black amphiboles and greyish white feldspars of the same size. Microscopic features. Name of rock: metadolerite. Texture: ophitic. Mineral composition: pyroxene, green amphibole, plagioclase, biotite, opaque mineral. Only a small amount of augitic pyroxene (based on Y/C extinction angle of 40°) can be found as a relict mineral in green amphibole (uralitization). Hypidiomorphic tabular amphibole with green - pale green pleochroism contains opaque mineral as inclusion. Composition of amphiboles is hornblenditic, based on a y/c extinction angle of 20-25°. The idiomorphic-hypidiomorphic 0.5 mm large plagioclase has oligoclase-andesinic composition based on Michel-Lévy extinction method. Biotite occurs as rare inclusion in plagioclase. It has a strong - colourless-brown - pleochroism. Based on microscopic features, the opaque mineral is ilmenite. The skeletal crystals with a size of 0.125 mm are turning into leucoxene (Photo Plate VI 13). Metamicrogabbro-dolerite Sample nr. 7. was classified metamicrogabbrodolerite. Macroscopic features. Hard, fine grained, blackmottled, dark green rock. Microscopic features. Name of rock: metamicrogabbro-dolerite. Texture: blastoophitic. Mineral composition: pyroxene, plagioclase, apatite, opaque mineral. Idiomorphic-hypidiomorphic 0.5-1 mm large pyroxene of diopside-augitic composition based on 30-35° Y/C extinction angle. It often turns into chlorite. Hypidiomorphic 0.5 mm large albite often turns into pumpellyite, rich in Fe (colourless-green pleochroism), clinozoisite, seriate (saussuritisation). Pumpellyite in the matrix turns into epidote as a results of rise in temperature of metamorphism. Idiomorphic apatite occurs as 0.5 mm long laths. Ilmenite can be found as 0.25 mm long skeletal crystals. It turns into titanite (leucoxenisation).