Rhodochrosite Specimen with Galena and Pyrite (Copyright 2012 Th' Gaussling)
Rhodochrosite is a mineral composed of MnCO3. The specimen above is in no way exceptional, other than as a curio. The mass is comprised of rhodochrosite, galena, pyrite, what looks like quartz, and possibly a trace of a gold colored metal.
The photo below shows the galena, or PbS.
Same sample as above, showing the galena. (Copyright 2012 Th' Gaussling)
The photos were taken with a USB microscope.
Lamentations on Chemistry 
Did you collect them? Where?
A rock shop in Leadville. I think the sample was from Alma, CO. This place is well known for rhodochrosite.
http://www.minfind.com/article-6.html