And ice, mast-high, came floating by
As green as emerald,

from Samuel Taylor Coleridge – Rime Of The Ancient Mariner on Rap Genius

Meaning

The ice could possibly be green due to algae. It could also just be ethereal imagery building up to the more…acid trippy events in the poem.

http://en.wikipedia.org/wiki/Ice_algae

To help improve the meaning of these lyrics, visit “Rime Of The Ancient Mariner” by Samuel Taylor Coleridge and leave a comment on the lyrics box