I just happened to be browsing the cranberry topic when I saw this, so I thought I'd add a quick comment. At that time in 2008, the holy grail of marble making was lutz - everybody wanted to run pure gold aventurine, but it was very difficult to do, easily burnt. Some of the oxblood in the run- both red and burnt - no doubt came from the copper flakes (lutz) dumped into the top of the furnace that just got too hot or reacted badly (I'm no glass chemist.) There was also some bright yellow glass used that undoubtedly added similar effects. The black/gray on these cranberries? Honestly after eight years and a half years I don't remember, but I think it was likely lutz, or possibly black aventurine, but I'm not sure there was much - if any - of that. Lots of green a/v, some blue, and lutz. I don't think yellow would have been added to red glass, or purple - another color that shows up in later examples, notably the parrot. Just FYI.