Just ask, and I can tell you, with the possible exception of some of the SA stuff (I've not played a gargoyle).
Medable automatically:
Leaf armor (elf-only)
Leather armor (without the word studded)
cloth items
masks
circlets
Medable with the term "Mage Armor" as one of the properties:
All other metal armor (other than circlets)
Studded (Leather) armor
Bone armor
Hide Armor
woodland armor
stone armor
Helmets
Artifacts & minor artifacts: Compare the item to existing items, as the item it most resembles (minus its special coloring) is what indicates whether it is medable or not.
Examples:
Voice of the Fallen King (Doom Artifact): Leather gorget, therefore medable
Jackal's Collar (Doom Artifact): Plate gorget, therefore not medable.
Inquisitor's Resolution (Doom Stealable): Plate Gloves, not medable
Stormgrip (treasures of Tokuno major): Leather Ninja Mitts, medable
Violet Courage (Minor Artifact): Female Plate, but since it is Mage Armor, it is Medable
Bronzed Armor of the Valkyrie (fishing): Is graphics for a leather Bustier, colored bronze (like a pair of bronzed baby shoes), so is medable.
Weapons and shields allow passive meditation, but require the "Spell Channeling" property if you intend to hold them while actively meditating (i.e. actually using the skill, as opposed to what regenerates over time if you do nothing) or cast magery (and mystic?) spells.