Let’s start with Darksteel Citadel, your run-of the mill land that’s also an artifact. Because it always has the “Artifact” card type, it can’t activate any abilities. It can’t even tap for mana, because unlike Pithing Needle, Stony Silence doesn’t make any exceptions in determining what abilities it shuts off.
Next we’ll move on to Inkmoth Nexus, the new and infectious kid on the block. Stony Silence cannot prevent Inkmoth from turning into a creature, because it doesn’t gain the “Artifact” type until that ability resolves. Once it’s turned into a creature, though, it stops Inkmoth from re-activating that ability (not very useful) and stops it for tapping for mana (again, not the most efficient use of your mana). Attacking is not an activated ability, however, so it can still attack (and tap as a result of that).
Last but not least is Blinkmoth Nexus. As with Inkmoth, Stony Silence can’t stop your opponent from animating their Blinkmoth, but it stops the animated land from tapping for mana. Importantly, though, Stony Silence will also shut off Blinkmoth’s pumping ability when it’s animated, so your opponent cannot animate Blinkmoth, block a creature, and have it pump itself to a 2/2. Your opponent would need two Blinkmoths to pull off that feat, one to become an artifact creature to block, and one to remain a non-artifact, non-creature land to pump.
Today’s Rules Tip written by Jen Wong