https://www.curseforge.com/minecraft/mc-mods/mekanism

• Osmium Material
  • Upgrades stats to be more inline with Mekanism tools
  • Adds "Kinetic" trait to Osmium
    • When using the tool, a single energy using item gains small recharge amount
• Adds "Glow Up" modifier
  • Adds glowing outline to hit entities, 30s per level

Quote from Aquifel7 on CurseForge:

Historically, oldschool Tinkers had it. Primary new material in Mekanism is Osmium, but you could also make Refined Obsidian and Refined Glowstone, along with 'Osgoglass' which was an alloy of all three. Osmium gave you extra durability and increased XP gain, Refined Obsidian gave you extra durability and sometimes prevented durability loss, Refined Glowstone made nearby entities glow and increased your critical hit rate. Osgoglass let you auto deposit blocks you mined into a linked inventory which was cool, but weird? Also, of course, we don't have to follow history.

For me, refined obsidian makes sense as a generic harder tool metal, its pretty, but kinda boring and there's no real 'lore' there. I think Osmium would be cool if it had some kind of interaction with RF/energy since that is kind of Mekanism's thing (Hits with this weapon recharge items in inventory? Lifesteal kind of but for things w/energy requirements? or maybe it regenerates energy passively? solar powered?). Refined glowstone could be interesting, it would make sense for it to somehow interact with light.