Originally Posted by: chrischch 
Hard to see in the pics but its most likely some sort of pyrite. Lammerlaw will have a better idea. He's the expert on such things around here. :)
I wish the rest of the world had that much faith in me!
To be honest I dont know - firstly one needs to see it close up and to know where it originates from. You are from the top of the South so I make the assumption that it is from up there.
A silvery colour metal could well be Platinum or Osmiridium and the fact that it remains with the black sands indicates that it is heavy like platinum. The pink tinge might discount that though but then again the pink tinge might be discolouration from another mineral. If one of the small pieces is placed under a stereo microscope can you determine whether the pink tinge is a coating or the natural colour of the material itself?
Heavy and pink might also be cinnabar but cinnabar would not be mistaken for a metal and is more likely to be a darker red. I am not aware of the existence of cinnabar in the Nelson district.
A lead grey sulphide of Molybdenum does occur in the Takaka District and Aorere River to the best of my knowledge. There is also a red coloured oxide of zinc up near Takaka somewhere but once again it wont have the appearance of your samples being an oxide.
I remember of a mineral known as Richmondite which was found up that away - I am pretty certain that it was comprised of lead, silver and copper but I have never seen it. The copper could give it a copper tinge though I would assume.
I dont think that it will be a copper or iron pyrite though as these tend to be more a yellow colour and even have a greenish tinge, especially Chalcopyrite which is a Copper pyrite. Iron pyrites is also more likely to be of a more cubic crystal structure than Copper pyrites which seem to be of finer grains and doesnt seem to come in the nice cubic form of Iron pyrites.
Although it often has a blue tinge to it one mineral which often looks silvery is Galena but once again the pink tinge more or less discounts that. Ihave never got Galena in a pan or sluice box but I have found it in situ.
All guesses and fairly wild ones at that.
If I ponder some more I might remember some of the other minerals from up that way which might vaguely fit the bill as they say - there were so many that years ago I wanted to move up there to pillage, plunder and scavenge the countryside in my quest for rocks and minerals.
