From: Manfred Clauss, The Roman cult of Mithras, p.67-8:
Among the elementary necessities -which thus also symbolised life - promised and bestowed by Mithras is the water that he caused to flow from the rock. Just as the god himself gives life, so too does the rock: the upper rim of the rock is decorated with flowers on a relief from Bingium (Bingen) in Germania Superior (V 1240, fig. 28).
Fig. 28. Bingium/Bingen: rock-birth relief. Euboulus describes Zoroaster's first cave in Persia, dedicated to Mithras, as 'flower-strewn and furnished with springs' (ap. Porphyry, De antr. nymph. 6) (see also fig. 45).
Statue in sandstone (H. 0.22 Br. 0.24 D. 0.12) found together with two altars in
Amtstrasze 6 in 1922. Here was probably a Mithraeum. Bingen, Museum, Inv.
No. 2462. I am greatly indebted to Dr. Gebauer, the Burgomaster of Bingen, for
sending me information about these monuments of his town.
Behrens in Germania VI, 1922, 82f and fig.; REA XXVI, 1924, 137; AJA
1924, 344; Esp. Rec. Gaule VIII, 109 No. 7418 and fig.; RRS V 225 No. 6;
Koepp, Germ. Rom., Pl. XXXVII, 2; Behrens, BL, 20 No. 1 and fig. 31. See
Naked Mithras being born from the rock on which a coiling serpent. The
transition of the rock into the body of the god is indicated by a wreath of large
flowers. The god's head and the upper part of the arm with the hands are lost.