Commercial lithium aluminium hydride is a grey compound, which loses a lot of reactivity the darker it is. Luckily you can clean it up to get the reactive white compound and the separated grey contamination. Over some time, however, it is said to slowly convert back to the grey form (at least this is what I read, I haven't watched clean samples turn grey again yet).
My question is, what is this contamination? I remember to have heard somewhere that it may be elemental aluminum, which forms by decomposition. And in fact, the thermal decomposition really yields aluminum as a side product. But I cannot find any reliable source I could quote for my thesis. Does anyone have a paper or book that actually mentions the grey contamination?