Chalcedoy & Unknown from Batallones Hill, Torrejón de Velasco, Madrid, Spain
This is a really amazing specimen and it is not only because of its color contrast but also because of its intense glow after SW the matrix stays blue.
Most of the samples that I have collected in this deposit are Flint, covered with chalcedony and some aragonite, however only this one and another have this long phosphorescence.
Size 8 x 10 cm
SW - NL.
Click on the link to see this effect larger!!!