Better than eye clean. If you look inside the stone in the magnified video and photos you’ll not see any inclusions present. No abraded edges on the facets. I do not have a certification stating natural cobalt but I believe this one is cobalt spinel. I guarantee it is natural. Displays the rare color change of cobalt spinel blue to violet depending upon the light source. Nice elongated cushion cut on this stone. Very symmetrical cut nicely shaped.

Sri Lankan spinel gemstone.  I try to price my stones below other sellers and try to make sure all customers are getting a true gemstone at a bargain price.  
There is an article on this site about blue spinel titled “The rarest of them all”.  It is located in the learn section under Additional Gemstone Information.  
Spinel is rarely treated or heated as it naturally comes without many inclusions and heating does nothing to increase the beauty of the stones.  
Spinel is rapidly becoming more popular.  I’ve heard many gem affectionados state it was their favourite gemstone.  It was once thought to be sapphire or ruby depending upon the color.   The imperial crown housed in the tower of London has a large red spinel which was once thought to be a red ruby.  It is named the Black Prince’s Ruby and has a recorded history dating back to 1366 AD.
Cobalt is the main colorant in blue spinels and are especially rare.  For me I prefer them over sapphires.  The better price, less inclusions and lower cost make it the better value.  It is also a hardness of 8 which is only slightly under sapphire so is good for everyday wearing.