D&D 5E Adamantine Weapons?

[pukunui]

Nothing official yet, sad to say.

Now we have something official, thanks to Xanathar's Guide. Adamantine weapons deal auto-crits to objects.

EDIT: Ninja'd!

 

[Yardiff]

In my Homebrew I have made it exceptionally hard to work with adamantium, but what I have agreed to, and I think is cool is im allowing adamantine weapons to be classed as light weapons because of its extra hardness ... less material is needed to create a versatile weapon.

In 3e adamantium was a heavier metal(armor gave damage reduction based on size, weapons were I believe considered magical and hard to break) and mithril was a lighter metal(armor/weapons was considered one level lighter).