It seems like some items, after you drop them to the ground,
crumble:
<590 HP 756 MA 479 MV || 5 AM civilized> n
An Eerie Cavern
[Exits: east south]
<590 HP 756 MA 475 MV || 5 AM civilized> drop knapsack
You drop a cowhide knapsack.
..........
You get a cowhide knapsack.
<431 HP 762 MA 463 MV || 7 AM civilized>
<someone> has arrived.
<431 HP 762 MA 463 MV || 7 AM civilized> wear all
You wear a cowhide knapsack about your body.
....
<431 HP 762 MA 463 MV || 7 AM civilized> l
An Eerie Cavern
......
<368 HP 733 MA 445 MV || 8 AM civilized>
<someone> leaves east.
You follow <someone> east.
The Outer Veil
[Exits: north east south west]
<someone> is here.
A cowhide knapsack crumbles into dust.
<368 HP 733 MA 441 MV || 8 AM civilized>
<someone> leaves east.
You follow <someone> east.
The Outer Veil
------------------------
Not all items crumble - along with knapsack, I dropped all my
equipment - and it didn't crumble.