Sangat,
There is mention of nidhi/ridhi/sidhi in Gurubani, which can be taken as good as miracles!
Also, Gurubani talks about these:
"Sabh Nidhaan Das Ast Sidhaan Thaakur Kar Tal Dhariaa."
"Tudh Vinn Sidhee Kinai Na Paaeeaa"
In one discussion on sikhpal.com, it came up with following...