Hedgehogs are hibernating and survive the hostile environment of the desert1. Thus, these amulets (many are seals with signs under their base) have a strong connotation of rebirth. They occur as early as Naqada II and are not exclusively in green colour1

Hedgehog – Blue glazed steatite Approximate L 1.2 Middle Kingdom Dynasty 12 Penn Museum #E9206
Hedgehog – Blue glazed steatite Approximate L 1.2 Middle Kingdom Dynasty 12 Penn Museum #E9206

Blue glazed steatite Approximate L 1.2 Middle Kingdom Dynasty 12 Penn Museum #E9206

Hedgehog – Blue glazed steatite on linen string L 0.9, W 0.6, H. 0.5 Middle Kingdom mid-Dynasty 13

Blue glazed steatite on linen string L 0.9, W 0.6, H. 0.5 Middle Kingdom mid-Dynasty 13 MET #22.1.301

Reference

1Andrews C. Amulets of Ancient Egypt, 1994, p. 64 and Figs. 54a,g