Near the end of Q2, Russell and Hamilton were starting flying laps when the former moved to the inside of the pit straight to grab a tow from Ferrari's Carlos Sainz, and then moved back onto the racing line.
But Russell appeared to be unaware that Hamilton behind him was also on a flyer and was about to overtake him on the outside when his team-mate inadvertently closed the door.
Hamilton had to take avoiding action with his left wheels on the grass, but still made contact with Russell and broke his front wing endplate in a collision that could have had much worse consequences.
On the radio, Hamilton said: "George just backed off, that was really dangerous."
The FIA stewards summoned both Mercedes drivers to review the incident, investigating why Russell's "car 63 normally changed direction directly causing impact with car 44" on Barcelona's start-finish straight.
When asked if the incident was simply down to a miscommunication, Russell said: "Yeah, pretty much. I wasn't even aware he was there.
"I was starting my lap, trying to take the slipstream from Sainz and fortunately, nothing bad happened."
The incident topped a messy qualifying session in which Russell struggled to get any grip from the tyres and faced a lot of bouncing. As a result, his 12th position on the grid was no surprise to Russell.
Source: Autosport