Does anyone have some insight into cleaning, and or polishing marble or slate clocks? As you can see in the picture this case has lost luster and has som spots on it.Maybe this has been discussed before and someone could point me to a previous discussion thread. Any info would be greatly appreciated.

That's a fine looking clock Ken,

I've tried numerous methods, and have concluded that boiled linseed oil applied generously, wiped off smooth, and left to dry overnight or for a couple of days even is the best solution I've found so far.