DDancer is very good at identifying materials, much better than me, and probably has a much much better education than me on minerals and such, I do not consider myself any kind of expert on these things, so take my opinion with a grain of salt. The "fresh" looking chip (on the tip) is concoidal (spelling?), just like chert would be, but most the chert I have dealt with is not as grainy when it "chips" out, it is usually more "slick" or "glassy" looking. That does not mean it "isn't" chert, but it would be a really low quality chert, and I say this because of how "grainy" the material looks in that fresh break. This is just my observation!
IAMZIM your observations are as good as mine I only said it what it appears to be for me. Your correct in that cherts generally have a smooth glassy appearance when chipped though I have had low grade stuff thats more like what I'm seeing. The op says this bits from New Guinea and that its volcanic in nature so chert is out I'm not familiar with any volcanic material like that presented.
The thread that the rock tool comes up in is pretty informative though.