Although this specimen was labelled as quartz and calcite on kutnohorite from Broken Hill, New South Wales, the calcite was not that easily seen (Hidden Collection!). That is, until hit with a UV torch! Then the brilliant red shone through.
The red fluorescence response is due to the presence of the activator manganese, as Mn2+. Under longwave UV, the response is quite good, but not as intense as when the calcite is hit with a Medium Wave UV light source!
Below: Quartz and calcite on kutnohorite. Width of view 9mm. Medium Wave ultra violet light. Click on the image for a higher resolution version.
Below: Quartz with pyrite inclusions on kutnohorite. Pyrite cubes on the surface of both minerals too. The calcite is on the back of the quartz, so not visible here. Width of view 9mm. Click on the image for a higher resolution version.
Below: The whole specimen in a 33mm square Perky box.
The kutnohorite looks like Japanese ç´ éºº.