Acta Musei Moraviae

Moldavite-bearing sediments near Lukov in the vicinity of Moravské Budějovice, Western Moravia

Between 1998–2005 several moldavites have been collected in two new localities near Lukov. They are olive-green in colour and have angular to subangular shape with lustrous and mat surface. The chemical composition of one sample shows similarity to the average Moravian moldavites (mainly Ca/Ti ratio), but Si and Ti content are consistent with Bohemian moldavites. Sporadic lechatelierite is the only inclusion. The source of moldavites near Lukov is Middle-Upper Miocene deluvio-fluvial clay and/or sand dominated sediments with gravel admixture (so-called strewn-field sediments). The sediments are poorly sorted and contain mainly subangular quartz and quartzite transported over relatively short distances, but well rounded pebbles redeposited from older sediments are also present. During younger transformation, especially in Quaternary age, primary fine-grained strewn-field sediment with short transported moldavites passes into residual gravels. Brown fragments of ferrolite abundantly occur in both localities. Typical opaque mineral in these sediments is maghemite (brown, magnetic granules and pebbles). Assemblage of heavy minerals (ilmenite, rutile, garnet, sillimanite, spinel) is similar to the underlying gneiss, and its older sedimentary cover (andalusite, kyanite). These sediments could be locally redeposited by fluvial transport of previous Rokytka stream and finally covered by loess.