To my big surprise, the wider Rotterdam area (Maasvlakte, Europoort, Botlek, Hoek van Holland, Maas Dykes) offers nice possibilities to find minerals. As the harbours are build with huge amounts of bolders and stones of different sizes and sources, one can do amazing finds.
Especially the Zirkon that I found is quite special and in good quality. As the localities are not always very accessible and the sites are not endlessly producing due to lack of natural sources, exact locations are not given. Most material originally comes from a few specific quarries in Norway, Germany and Belgium, in many cases the original location could be traced back via harbour authority and public archives. Amongst them are Quenast (B), Mayen Area (Vulkan Eifel, D; almost for sure Rothenberg!), Ourthe area (B), and Larvik (N). The Epidote originates from few totally different sources. You may also watch the video! https://vimeo.com/681536430