> Where did you get that from?

Well, the texture is yours :-)
I just thought that the chunk should look the same as the gold deposit it was mined from. So I applied the texture from this post and got the chunk you can see above.

> Perhaps it's applicable for material too

It is 100% applicable :-)

> Do you care to create material chunk graphics in 192x192 (3x 64x64) for all materials?

I thought we already have some good models (personally I like rock very much. Ore and coal look nice too - but, again, the sky is the limit). We had ice here (nice shape by the way, maybe a little more transparent).
Also I like loam as it is here (maybe it can be made brighter) and a wooden "log" to be something like this (one of my favorite example of changing the CR graphic - still unimplemented).
But this models (and ideas behind them) should be somehow collected in one place.

> Then we have them in a similar style

Well, I see what I can do but it would probably take some time (Busy, busy :-( my bad)
At least I will post the 192x192 of this one in a day or two

> Currently it looks like material chunks are gonna stay sprites

What about dynamite? It looks realy awfull when you zoom in