When written as a standalone kanji, the following metals have longer, "full" names (based on their colour):
- [金]{こがね} → こがね
- [銀]{しろがね} → しろがね
- [銅]{あかがね} → あかがね
- [鉄]{くろがね} → くろがね
In my Japanese Bible, there are various places where they appear in lists of materials, etc. I rather prefer to read them by these full names, but I don't know if that is correct or not. Are these full names ever used in modern Japanese? If so, in what kind of situations are they read this way?
Your aesthetic preference is one thing, but whether or not others would understand what you said is another.
Most adult speakers would surely understand こがね but not too many would understand the other three. Even with こがね, you will sound very strange though we know what it means. We just do not use the kun-readings for these metal names in our daily lives.
The kun-readings do sound cool and I like them myself, too, but they are pretty much reserved for use in literature and the world of blacksmiths. If you still want to use them, you would probably have to say the words in their on-readings first, briefly explain your preference for the kun counterparts before you start using them.
Trivia Information :
If you say しろがね out of nowhere, more people will think you said 白金 -- which is an upper-class section of Tokyo -- than those who will think you meant "silver". 白金 is officially read しろかね but most people pronounce it しろがね. The posh ladies from that area are called シロガネーゼ. A cool word to know that Genki will not teach you.
