2) from Staric hard coal underground mine (approximately 15 km S from Ostrava) is predominantly composed of subangular
to angular monocrystalline quartz grains with average grain size ([M.sub.d]) of 0.36 mm.
The soil mineral coarse fraction had varied sizes and well-preserved edges (subangular
to subrounded), indicating low contribution of the sedimentary material to the soil formation.
The petrographic study reveals the fine to very coarse quartz grains along with subangular
to subrounded grain shape and poor sorting.
Transverse equatorial sections show elliptical, subangular
, triangular, and nearly circular endocarp outline (Fig.
Conchoidal features of various sizes (Figs 5, 6I), along with straight and arcuate steps (Figs 5, 6J) and parallel striations (Figs 5, 6K), occur on angular and sometimes on subangular
The dominant size for these subangular
quartz grains is 30-50 [micro]m (e.g.
It comprised various dimensions of subangular
siltstone gravels together with silty clay and clay; the gravel content was approximately 10~70% (Figure 2(a)).
Frequency (%) (a) Cobble 12.61 Pebble 70.54 Coarse sand 5.36 Medium-fine-sand 9.13 Silt mustone 2.36 (c) Frequency (%) Well sorted 1.92 Medium sorted 11.54 Poor sorted 86.54 (d) Frequency (%) Round 5.77 Round subrounded 69.23 Subrounded 8.65 Subangular
subrounded 6.73 Subangular
round 8.65 Angular 0.96 Note: Table made from bar graph.
(3) WE = weak; ST = strong; MO = moderate; VST = very strong; FI = fine; FM = fine and medium; VM = very fine to medium; MC = medium and coarse; ME = medium; CO = coarse; VC = very coarse; EC = extremely coarse; GR = granular; SB = subangular
blocky; AB = angular blocky; PR = prismatic.