very, very strange.
for example today about Retarget:
Block            Time                           Difficulty
959372   10/23/2015 18:09:12   4,6368
959371   10/23/2015 18:07:05   4,6368
959370   10/23/2015 17:58:01   4,6368
959369   10/23/2015 17:53:23   5,1005
959368   10/23/2015 17:51:16   5,1005
………………      
959341   10/23/2015 13:49:36   5,1005
959340   10/23/2015 13:42:41   5,1005
959339   10/23/2015 13:41:49   5,6105
959338   10/23/2015 13:41:20   5,6105
………………      
959317   10/23/2015 10:49:24   5,6105
959313   10/23/2015 10:45:53   5,6105
959305   10/23/2015 10:28:40   6,1716
959299   10/23/2015 10:25:51   6,1716
959292   10/23/2015 10:13:12   6,1716
959289   10/23/2015 10:11:17   6,1716

and finding block not one per minute depending on the statistics

- 6.77 coins per block, just like 6.77gms of gold in a real doubloon!
- Digging can continue until 8 million coins or 5 years, whichever comes first.