Coleridge's Alchemical Mariner

This is an extract and symbol key from the celebrated alchemical text by Kenelm Digby, A Choice Collection of Rare Secrets (1682). I bung it up, here, because I'm doing some work on 'The Ancient Mariner', and I discover that the alchemical symbol for copper is the same as for 'Venus', there.  So after passing through the iron-grey land of ice and snow the mariner's craft enters the Pacific [107-14]:

Down dropt the breeze, the sails dropt down,
’Twas sad as sad could be;
And we did speak only to break
The silence of the sea!
All in a hot and copper sky,
The bloody Sun, at noon,
Right up above the mast did stand,
No bigger than the Moon.

I've always taken the copper sky as merely descriptive of colour, and perhaps of smoothness and apparent hardness; but maybe there's an alchemical gloss here: the ship has moved from the martial, cold, vigorously windy, iron-coloured masculine Atlantic into the feminine, hot, lassitudinously windless, venusian female space of the Pacific; from Death to Nightmare-Life-in-Death.