Maybe a weapon made of ferroplasm will do?
Mined from secret locations in the Astral Plane, this malleable metal holds its shape only in the hands of a psionic being. When an item forged with ferroplasm is unattended or held by a nonpsionic creature, it melts and temporarily loses all special powers. But when wielded by, psionic creature, such an item immediately springs bad into its true shape and regains all abilities. In its proper form, a ferroplasm item glows with a violet light (illuminating a 10-foot-radius), unless the item’s owner mentally quenches it. In an area where psionic powers do not function, it collapses as if in the hands of a nonpsionic creature. ...
Weapons fashioned from ferroplasm have a natural enhancement bonus to attack and damage.... These bonuses do not stack with other enhancement bonuses. Weapons or armor fashioned from ferroplasm are treated as masterwork items with regard to creation times, but the masterwork quality does not affect the enhancement bonus of weapons....
Ferroplasm has hardness 20 and 40 hit points per inch of thickness when in its true form, and a hardness of 5 and 10 hit points per inch of thickness when soft. (Psionics Handbook 138)1
A weapon made of ferroplasm that deals 1d4 or 1d6 points of damage gains a +1 enhancement bonus and costs an additional 2,500 gp, while a weapon made of ferroplasm that deals 1d8, 1d10, or 1d12 points of damage gains a +2 enhancement bonus and costs an additional 7,500 gp.
Alternatively, how about a sentira weapon?
This bizarre material is wrought by Chosen, Inspired, and (rarely) kalashtar who use powdered crystal and the power of their thoughts and emotions, also drawing on the essence of Dal Quor. Sentira items are literally grown into their final form. They have an organic,
whorled appearance, much like horn or shell, with a shimmering, opalescent surface. Color varies based on the emotion used to create the particular batch.
Sentira is lightweight and almost unbreakable. Because of its resonant properties, it is an ideal material for emotional armor. For purposes other than those described in this chapter, sentira is treated as mithral.
Sentira can be formed, sculpted, and repaired only by psionic creatures that have the Craft (sentira) skill. Such craftspersons, known in Riedra as thoughtweavers, must expend 1 power point for each day of work on a sentira object, whether building or repairing it. (Secrets of Sarlona 135)
Sentira is, you'll note, made of "powdered crystal" but "treated as mithril"--I don't know if that's close enough for the DM (or a chem professor), but at least the description mentions another metal, albeit a fictional one. Interestingly, although no statistics are given for making weapons from the sentira, everything else in Secrets of Sarlona is made of sentira (e.g. armor, mosaics, gates, public art installations, passports, entire buildings). It'll be up to the DM to determine the price of sentira weapon. I suggest he be guided by the special abilities and costs of emotional armor (137-8).
- Yes, the Psionics Handbook, not the Expanded Psionics Handbook. The special material ferroplasm doesn't appear to have been republished for Dungeons and Dragons 3.5 making the Psionics Handbook version oddly Dungeons and Dragons 3.5 compliant.