a game of stealing creation lasts 18 minutes with a 2 minute cooldown, and you can easily get 20+ points in that time. by my third match i'd already locked in getting 22 points a game. if the sacred clay tools last more than 20 minutes of mining your target ore, its worth your while to get them. someone should mine 100 iron, 100 coal, and 100 gold, to see if it is time based, exp based, or items completed with the tool out. if its time based and lasts more than 20 minutes in total, then its 100% worth using them. if its exp based then it is more worth it for every day miners that are mining slow ores like adamant and mithril, since you'll be gaining exp slowly anyway, you wouldn't fill up the exp limit in 20 minutes of mining with it. if its ore count based, then its only worth it for power mining if it has a huge item cap. if its small, say 250, you'll mine far more granite than that in 20 minutes, so you'd just waste your time at sc.
however, stealing creation is devilishly fun, and you might want to factor that in

EDIT: the items are based off a set amount of experience per tool. tested with woodcutting, and you get 16k total bonus exp per tool. can you wc 16k exp in 20 minutes?

you can find out how much exp your tool gives you for mining pretty easily. use a new tool to mine a rock that gives you a regular incriment of exp. 50, 100, something that divides into 100 with a simple fraction remainder. mine 1k exp worth of ore if possible (will be 2k with the tool on) then track what % it is at. then: 1000/[100-(%left)]x100 = how much bonus exp you can get.