I brought this up in the "boards are down" comments, but just want to get the input of everyone, who may not have been following that.
One of my players, a barbarian, wants to get a Lesser Ironward augment crystal (MIC) to put on his armor. He's also wanting to get a mithril breastplate. A lesser ironward crystal only works on medium or heavy armors (it grants DR 3/- for up to 30 points absorbed per day). It specifically states it stacks with "similar DR" - ie, the Barb DR.
Just to examine the wording:
"A lesser iron ward diamond functions only when attached to medium or heavy armor."
"Most mithral armors are one category lighter than normal for purposes of movement and other limitations. Heavy armors are treated as medium, and medium armors are treated as light..."
It is treated as light for movement and other limitations. The question then is, what are the other limitations? Proficiency? (ie - is a rogue proficient with a mithril breastplate?) Should the qualities of the ironward crystal count as a limitation?
A mithril breastplate counts as light armor for movement, but what other ways does it count as light armor, and does it ever count as medium armor for any purpose?
Can this augment crystal be used on a +1 mithril breastplate?