...they don’t care who they’re buying it from....We had ~s. They are supposed to be $20 rocks....in a tin, and we’ll actually let them take out the rock that they want...San Bernardino Co CA Sheriff’s Dept Narco Det Paul Gallant

"Rock" of course, refers to a small crystal of cocaine. I get forty thousand hits on "big rock" pert cocaine but frankly don't have the patience to wade through all these hits

Can anyone elucidate

Thanks all

Edited to cite usage

What's the question?

it comes in chunks, dale, that look like rocks.

eta: So I understand. I think they're called crystals too. But I gained the expression that in order to be big it had to meet a certain criterion, such as street price

geodes are rocks
geodes are crystals
rocks can be crystals
(sleet and hail are ice crystals that have formed into rocks--only they have special names)

hail comes in 'pea size' and 'golf ball size'--and sometimes bigger still. (i have never seen anything much bigger than a chick pea size hail)

rocks (crylized chunks of crack cocaine) comes in different sizes too.

yes, golf ball size(big rock) is going to cost more than pea size.--there is more!
(only pea size is big for crack cocaine, most of the rocks are smaller)

I once saw a plover's egg the size of a diamond.

Not to mention a golf ball the size of a hail stone.

Not to mention the third rock from the Sun.