My brother was trying to get his lego airplane from the shelf.
There was no instruction from them of how much weight we can put on it.
I think it's the basic knowledge for construction or anyone that if they are going to put a marble shelf on the fireplace, they had to put the support on the bottom due to the weight, but they thought it was not necessary. The entire shelf was held by 5 large nails.
Besides, the need for the shelf is to hold decoratives, and I have weighed all the broken pieces, less than 10 lbs, so this amount of weight is considered to be not acceptable on a fireplace shelf?