I had an idea to replace the Lara Necklace I was wearing for a while (until I loaned it to my sister). And that is the Wraith Stone worn by Amanda Evert in TRL and TRU.
I did some general research. It hasn't shown up on the Replica Props forum, but there have been a few Amanda cosplayers here and there (including an excellent Young Amanda cosplay I spotted at DeviantArt. She must have hand-embroidered the shirt -- it looks perfect.) There haven't been, to my eye, any decent recreations of the Wraith Stone.
It has been illustrated by several fans (there's a surprising amount of Amanda fanfic out there. I didn't realize so many people would find themselves leaping to her defense and trying to show she wasn't really the whiny, self-centered, back-stabbing brat depicted in the games). But these depictions have such a range, it is hard to look at them as building upon what was revealed in the games.
So to the source. I viewed every minute of cutscene from both "Legend" and "Underworld." (There's no use viewing gameplay; you don't play Amanda directly, and as Lara you rarely get close enough to her to see the Wraith Stone properly). And as is far too typical for Tomb Raider, the prop is inconsistent.
As far as I can tell, there are at least two in-game models in "Legend." Possibly three, and you might or might not count the one she wears, as that is probably part of the character mesh. And they don't look particularly similar. However; they look more like each other than either looks like the in-game model visible in "Underworld."
In Amanda's character model and in all but the close-up model, the Wraith Stone is just a teardrop-shaped black rock with an elongated white skull pattern on it that looks bas-relief. In the close-up model, it is a purplish stone with a slightly more complex carving. (In the "Underworld" in-game model, it appears to be a clear turnip-shaped stone with a skull appliqué on one face.)
What attracted me to this prop is, in fact, only realized in one place; in the opening movie of "Legend" there is what appears to be the Wraith Stone -- rendered in the same style as the Excalibur prop central to that particular game, as if it might be an artifact of the same culture.
The Excalibur Fragment depiction is of a dark grey-and-black material with strong isotropy; it catches the light in complex ways as it moves, like certain polished minerals. It is speckled, as well, with well-defined blobs of green. Now, this may be an artifact of the limitations of the in-game render engine and intended to depict greenish glow issuing along veins/flaws in the stone. Or it may be intended literally, as actual gemstone-like green nodules.
In any case, despite the almost completely unique nature of this single reference, I am prepared to argue the limitations of in-game models and, more importantly, that this is a heck of a lot more interesting to look upon (and to sculpt), and, thus, this is the version I am going to take a shot at.
Of course me being me, one of the things that excites me (and this may not be the prop for it) is the challenge of doing those greenish glows not just with LEDs, not just with individual surface-mount LEDs, but with a self-contained driver circuit that will flicker them in an interesting and deliberate way. Of course that may mean interpreting the depiction more as flecks of light along full-length crystalline inclusions in the base matrix, but...hey, that's interesting enough to look at and way challenging to model and cast that I think it is a worthwhile direction to go.