Darksteel Axe
Artifact — Equipment
Indestructible (Effects that say "destroy" don't destroy this Equipment.)
Equipped creature gets +2/+0.
Equip 
Heavier than it looks, tricky to wield, guaranteed to last.
Daniel Ljunggren
Double Masters (2XM)
• #247Rulings
Although Darksteel Axe has indestructible, it can still be put into the graveyard for other reasons. The most likely reason is if it's sacrificed.
(wotc • 2013-07-01)
Darksteel Axe itself has indestructible, not the creature it's equipping.
(wotc • 2013-07-01)
Rulings
Although Darksteel Axe has indestructible, it can still be put into the graveyard for other reasons. The most likely reason is if it's sacrificed.
(wotc • 2013-07-01)
Darksteel Axe itself has indestructible, not the creature it's equipping.
(wotc • 2013-07-01)