D&D 5E (2014) Ruby of The War Mage question

[ManBagel]

So I have a question about the the Ruby of the war mage. Can it be used as an arcane focus when’s it’s not attached to a weapon? And if so can be used when not attuned as an arcane focus as long it is not attached?

 

[jaelis]

No, it only allows you to use a weapon as a focus; it's not itself a focus.

 

[ManBagel]

I might as well just use a staff then