Ok, so I made a simple add-on with copper gold and silver and some example items, and here's what I got:
[SUBMENU_START:Precious]
.Harvest copper ore. "Hunting Horn" [effort:2] [phys:arms,hands,stance] *COMMON* /40/ [noquality] [patch]
{[NEARBY_TILE:river]} 'Near rapids'
{[TERRAIN:hill]} 'mountainous terrain'
{*hammer}
[NAME:ore of copper]
[MATERIAL:stone]
[WEIGHT:1.2]
[PRICE:0]
[TILEGFX:bc-orepiece]
.Harvest silver ore. "Hunting Horn" [effort:2] [phys:arms,hands,stance] *COMMON* /50/ [noquality] [patch]
{[NEARBY_TILE:river]} 'Near rapids'
{[TERRAIN:hill]} 'mountainous terrain'
{*hammer}
[NAME:ore of silver]
[MATERIAL:stone]
[WEIGHT:0.06]
[PRICE:0]
[TILEGFX:bc-orepiece]
.Harvest gold ore. "Hunting Horn" [effort:2] [phys:arms,hands,stance] *COMMON* /1h/ [noquality] [patch]
{[NEARBY_TILE:river]} 'Near rapids'
{[TERRAIN:hill]} 'mountainous terrain'
{*hammer}
[NAME:ore of gold]
[MATERIAL:stone]
[WEIGHT:0.0025]
[PRICE:0]
[TILEGFX:bc-orepiece]
// roasting
.Roasted precious ore. "Hunting horn" *COMMON* /1/ \3\ [noquality] [patch:50]
{Ore of*} #0.06# [remove] [patchwise] [name:Roasted ore of %s] [naming:last word] 'Copper/silver/gold ore'
//{Firewood} (4) [patchwise] [ground] '+to pile with ore'
//{Firewood} (4) [patchwise] [ground] '(You need to light them on fire)'
[MATERIAL:stone]
[WEIGHT:0.05]
[PRICE:0]
[TILEGFX:bc-orepiece]
// smelting
// improved method
.Smelt precious ore. "Hunting horn" [effort:2] [phys:arms,hands,stance] *TIMBERCRAFT* %-20% -M- /1/
{Roasted ore of*} #1# [remove] [noquality] [name:Bloom of %s] [naming:last word] 'Roasted ore'
[MATERIAL:iron]
[WEIGHT:1]
[PRICE:0.01]
[TILEGFX:bc-ironbloom]
// Previous method
.Smelt copper ore. "Hunting horn" [effort:2] [phys:arms,hands,stance] *TIMBERCRAFT* %-20% -M- /1/
//{Bloomery*} [noquality] [ground] 'Bloomery furnace'
//{Fire} [noquality]
{Roasted copper ore} #1# [remove] [noquality] 'Roasted iron ore'
//{Charcoal} (8) [remove] [noquality] [ground] '+to mix with ore'
//{Bellows} '+for keeping the heat up'
//{Shovel} [noquality] '+for tending the process'
[NAME:Copper bloom]
[MATERIAL:iron]
[WEIGHT:1]
[PRICE:0.01]
[TILEGFX:bc-ironbloom]
.Smelt silver ore. "Hunting horn" [effort:2] [phys:arms,hands,stance] *TIMBERCRAFT* %-20% -M- /180/
{Bloomery*} [noquality] [ground] 'Bloomery furnace'
{Fire} [noquality]
{Roasted silver ore} #0.05# [remove] [noquality] 'Roasted iron ore'
{Charcoal} (8) [remove] [noquality] [ground] '+to mix with ore'
{Bellows} '+for keeping the heat up'
{Shovel} [noquality] '+for tending the process'
[NAME:Silver bloom]
[MATERIAL:iron]
[WEIGHT:0.05]
[PRICE:1]
[TILEGFX:bc-ironbloom]
.Smelt gold ore. "Hunting horn" [effort:2] [phys:arms,hands,stance] *TIMBERCRAFT* %-20% -M- /1/
//{Bloomery*} [noquality] [ground] 'Bloomery furnace'
//{Fire} [noquality]
{Roasted gold ore} #0.05# [remove] [noquality] 'Roasted iron ore'
//{Charcoal} (8) [remove] [noquality] [ground] '+to mix with ore'
//{Bellows} '+for keeping the heat up'
//{Shovel} [noquality] '+for tending the process'
[NAME:Gold bloom]
[MATERIAL:iron]
[WEIGHT:0.05]
[PRICE:10]
[TILEGFX:bc-ironbloom]
// coinage testing
.Generic coin. "Hunting horn" [effort:3] [phys:hands] *CARPENTRY* [noquality] /5/
//{*forge*} [noquality]
{Bloom of*} #0.02# [name:%s coin] [naming:last word]
{*iron hammer}
[TYPE:valuable]
[WEIGHT:0.02]
[MATERIAL:iron]
// COPPER
[PRICE:0.1]
// SILVER
//[PRICE:1]
// GOLD
//[PRICE:20]
// Previous method for coins or crafts
.Copper coin. (64) "Hunting horn" [effort:3] [phys:hands] *CARPENTRY* [noquality] /5/
//{*forge*} [noquality]
{Copper bloom}
{*iron hammer}
[TYPE:valuable]
[WEIGHT:0.015]
[MATERIAL:iron]
[PRICE:0.1]
.Silver coin. (4) "Hunting horn" [effort:3] [phys:hands] *CARPENTRY* %20% /3h/
{*forge*} [noquality]
{Silver bloom}
{*iron hammer}
[TYPE:valuable]
[WEIGHT:0.012]
[MATERIAL:iron]
[PRICE:1]
.Gold coin. (2) "Hunting horn" [effort:3] [phys:hands] *CARPENTRY* [noquality] /4/
//{*forge*} [noquality]
{Gold bloom}
//{*iron hammer}
[TYPE:valuable]
[WEIGHT:0.018]
[MATERIAL:iron]
[PRICE:20]
// weapon testing
.Precious spearhead. "Hunting Horn" [effort:3] [phys:arms,hands,stance] *CARPENTRY* /6h/
{Bloom of*} [remove] [name:Spearhead of %s] [naming:last word]
//{*billet} [remove] 'Good billet for the edges'
//{*billet} [remove] [noquality] 'Second billet for shape'
//{*forge*} [noquality] 'Forge or furnace'
//{Charcoal} (4) [remove] [noquality] [ground]
//{Bellows}
//{*anvil*} [ground] 'Anvil nearby'
//{*hammer} 'Hammer'
//{* tub of water} [noquality] [ground] 'Tub of water for quenching'
[MATERIAL:iron]
[WEIGHT:1]
[PRICE:0]
[TILEGFX:bc-spearhead]
.Precious spear. "Spear" [effort:1] [phys:arms,hands] *CARPENTRY* /3h/
{Spearhead of*} [remove] [name:%s spear] [naming:last word]
{Staff} [remove]
{Knife}
{Whetstone} [noquality] '+for final sharpening'
//original spear price is 43 arrows or so
// COPPPER
//[WEIGHT:5]
//[BLUNT_ATTACK:4]
//[POINT_ATTACK:6]
//[PRICE:30]
// SILVER
//[WEIGHT:6]
//[BLUNT_ATTACK:5]
//[POINT_ATTACK:5]
//[PRICE:60]
// GOLD
//[WEIGHT:7]
//[BLUNT_ATTACK:3]
//[POINT_ATTACK:6]
//[PRICE:100]
[SUBMENU_END:Precious]
Note that I fixed harvesting to hill + river for testing, couldn't find the original mountain + rapids adjacent to each other. This could be reduced to 1 with the use of optional nearby tiles, perhaps, but I'm not sure. They could also be removed if we create ore "flowers" with an appropriate rarity blooming in mountains or caves.
Roasting and smelting is condensed into a single recipe each. This could be combined with the iron ones, so it's elegantly solved.
I also have the material specific smelting I was using before, allowing more control.
I just created the generic coin, which will become copper/silver/gold coin depending on the material. The pricing and WEIGHT can be adjusted according to the comments below it. This can be applied to any craft I guess
I also have the material specific versions of the coins in particular.
Lastly I made an example spearhead an spear which can be made from these various materials. Again, the properties of the spear can be adjusted according to the material used. It will be iron spear, gold spear, silver spear, etc. The values are mostly examples.