A Ferrari spokesman said the Finn completed 47 laps, concentrating on development work after a rainy start to the day limited track time at the eastern Spanish circuit.
Raikkonen was the second fastest on the timesheets with a lap of one minute 13.529 compared to Alonso's best of 1:12.563.
Alonso stopped on the track with five minutes remaining of the session after what the Mercedes-powered team said was a minor oil leak.
Tuesday's test was the first at which all of the top teams were testing their new cars at the same time. Brazilian test driver Nelson Piquet junior was third fastest for world champions Renault in 1:13.550.
Photograph: Paul Gilham/Getty Images