On Sun, 18 Mar 2012 09:53:53 -0700 (PDT), tutall >
wrote:

>On Mar 17, 5:40*pm, Zz Yzx > wrote:
>
>> grain size doesn't determine bulk density. *Size sorting does. *i.e.,
>> if you fill a room with basketballs, there's a certain portion of
>> voids between the balls. *Fill the same room with volley balls,
>> softballs, baseballs, golf balls, marbles, or BBs, the void ratio
>> stays the same, as long as the balls are of uniform size.
>
>Forgive me, it's been a few decades since I've done this sort of math,
>and only got through one year of calculus. But is this saying that a
>10ft cube full of basketballs with have the same volume (not ratio) of
>void space as the same space filled with BB's?

That is correct. Fill a cube with basketballs, softballs, BBs,
whatever, the PERCENTAGE of void space (i.e., the total volume of the
cube minus the volume of the sphere; "porosity" in geologic jargon),
is the same, as long as the "packing" stays the same.

Look at this way: take a cube 1 foot square. Now stick a sphere
inside that just fits. Now, in your mind, make the cube/sphere bigger
and then smaller. The volumes of the cube and sphere change, but the
porosity (volume cube - volume sphere) stays the same. Now, stack a
series of said cubes/spheres side by side, up and down, make them
bigger/smaller, the volume ratios (porosity) are constant, again as
long as the packing arrangement stays constant.
>
>Am pretty sure this is wrong?
>
>> The bulk density differences are due to different crystal structures
>> and milling processes.
>
>Makes pefect sense.