A bracelet of clay allows players to minesoft clay instead of hard clay. The bracelet lasts for 28 charges (28 soft clay) before disintegrating. The player can see how many charges remain by equipping it and clicking "check."
It currently costs about 59.71 coins for each use of a bracelet of clay.
Exceptions:
When mining the soft clay rocks in Prifddinas, wearing a bracelet of clay produces two soft clay from each rock instead of one, although still at the expense of a charge.
A charge is not used when soft clay mined is directly delivered to the bank by a stone spirit.
If mining clay while a porter is equipped, the banked clays will be soft.
The effect given by freeing the Star Sprite comes in handy here as well, as players have a chance of mining 3 soft clay at a time, while only using one charge from the bracelet.
Bracelets of clay stack on each other in the bank, as charges are stored by player, not by bracelet. This is the same as how the ring of forging works.
If you equip the bracelet after you've already started mining clay, you will still get soft clay.
It used to be a free-to-play item, but temporarily became a members item. However, as of the update on 9th October 2017 it's back to being a free-to-play item.