I don't know what the globular shape is. It's not calcite, but it looks like silver star stone or grape stone from the cleavage surface? Buy it yourself and study it. The bottom rock is basalt. 

Our Mineral crystal Shop at Shantou,Guangdong,China
Our Wushan spessartine mine at Tongbei,Yunxiao,Fujian,China.
We can offer all kinds of chinese mineral crystals by wholesale or by retail.You are welcome to contact us in free time!
When in China, please come by for a visit. I would be very happy to meet with you!