We recently bought this set of rocks from National Geographic in order to write this review on it, to let our customers know if it is worth buying or not. 
 
Since we already have 90% of the rocks that came in the collection, of course we will sell them on so that they are back in circulation. We like buying from National Geographic because they put funds into STEM learning and games, as well as funding wildlife initiatives in the areas they help.
 
This piece of polished snowflake obsidian has the lovely dark black with recognisable snowflake patterns on it. It has a great shine.