According to Cornwall & Scilly HER Number: 1634 (go to Links) there are 3 cairns in Greenbarrow Downs Bronze Age Cairn Cemetery. Cornwall & Scilly HER Number: 1634.20 corresponds to Greenbarrow, a round barrow c. 150 yards SW listed separately in TMA. Cornwall & Scilly HER Number: 1634.30 describes a recently scheduled speculative stone mound located c. 35 yards NW of Greenbarrow. A grid search at SX 1303 7302 failed to find it amongst rough moorland tussocks. The remaining cairn, listed as Cornwall & Scilly HER Number: 1634.10 describes a round barrow at SX 1303 7302. Greenbarrow Downs NE is a grassy round barrow measuring c. 17 yards in diameter and 1.5 feet high with a central mound measuring c. 10 yards in diameter and 2 feet high. There is an Excavated Hollow in the centre of the cairn filled with reeds.
The OS map marks two cairns very close to the Greenbarrow. One is obvious to spot at SX131730. The other, marked at SX129730 didn't seem obvious to me.