Just discovered (before uploading) that there is another mod titled "Improved Craftable Circlets" which shares the core principal of this mod. My version does vary from the other mods and comes with a couple new features.

Also, this mod does not use nor modify any of the files from Improved Craftable Circlets, Craftable Circlets or JewelCraft. 

I initially wanted to use JewelCraft myself but was disappointed by its Steel Ingot recipe, and the further bloat that came with the mod. I even had a couple ideas of my own. This mod aims to keep the Steel's Iron and Copper (Corundum) crafting recipe intact while still offering to rename Corundum into Copper and allow the player to forge Circlets.

Features:

• Corundum ores, ore veins and ingots are now Copper (now the Steel smelting recipe makes sense). (Fix-sorta)
• Jade circlets are now Glass circlets and hence are crafted using Malachite.
• Blue Moonstone (texture) is now normal Moonstone. (Fix)
• Sapphire gemstones are no longer grey. (Fix)
• Onyx circlets have been renamed to Orichalcum and thus are crafted using Orichalcum.
• Circlet prices have been altered to match (or marginally improve on) the value of the items used in the recipes.
• Gems necessary for crafting need to be Flawless.
• Circlets have been renamed to fit the naming structure of necklaces and rings, e.g. "Gold Ruby Circlet" instead of "Gold and Ruby Circlet". (Fix)
  

Justification:
As Jade Circlets were green and metallic, unlike jade itself, I chose a similarly green-tinted metal to be used in its crafting recipes: Malachite. To make up for the blue tint I've retextured Jade Circlets to look like malachite and even renamed them to Glass Circlets, like Glass Armor.

I'm not going to add Onyx to the game, as this is my first mod (with no real mod developing experience prior), so as a placeholder I will be using Orichalcum instead of using Ebony. Ebony isn't very attainable early in the game and the only onyx circlet available originally had a value of 50, so I thought Orichalcum would be a valid substitute as a cheap green-ish gemstone, even if it's actually a metal.

The usage of Flawless tier gemstones is to prevent the player from mass producing the more expensive circlets for profit. It also wouldn't make sense for Jarls to wear such easily craftable jewelry.

Changelog
1.1:

• Sapphires aren't as bright anymore. Looks more fitting when compared to ruby and emeralds in circlets.
• Moonstone looks more like moonstone than a light-brown stone
  

1.0:

• Initial release.