http://www.antiquefarmhouse.com/miniature-crown-with-cross-under-glass-dome.html
How large is it ?? There is a similar styled one above but different materials !! My guess is that it is a souvenir type item !! May or may not be natural quartz !!
That is the only one I have found and found none like yours !! Is there anything written on bottom or anywhere ??
It is about 10″ high, about 6″ diameter. Showed the pictures to some local antique dealers, and none seemed to know or have seen anything like it. No markings of any kind.