How to use a block particle in /particles?
The /particle block <block> <position> <delta> <speed> <count> <normal|force> command is for the particle effects for when you mine the block, run on the block, etc.. You need to specify a block for it to work. For e.g.;
/particle block gravel ~ ~ ~ 0 0 0
This'll create a gravel block effect right under your feet. (it is recommended to leave delta 0 0 0)
/particle block glowstone ~ ~ ~ 0 0 0
This'll create a glowstone block effect right under your feet.
Hope this helps!