there are only 8 lava zones in the 16 squares of the Caves. I'd whack one quick whack in one, then once in another, and so on, with some of those being mana whacks or manual whacks.
And perhaps you need to buy the spell that helps with quest items. But it never takes me more than 20 or 30 Bushes.

maybe it's just luck or coincidence, but I whack in the Burning Lakeside every time and find it after just a few whacks.

of course, having insisted on that one zone, it took me two zones to find it!! **sigh** I whacked around the Burning Lakeside for awhile, then went to the Summit path and found it quickly...must be random. Hope I don't start having problems finding it! The heart of water is easy--just a few bushes worth.

The hidden Cave might not have Lava, but it's an 'inside' of the Caves vs an 'outside' part of the cavernous mountain region. I think that's the jist of it, in a cave not out of the caves.

I think you guys are going about this all wrong. I don't think one should view the Mana Statue in the same way as you view the Energy Statue. View it as an "extra boost" to be used conservatively, like you (hopefully) use the refills you get from fishing tokens. Don't just use it every week, use it during those weeks when you actually need it to finish something quickly. Optimize.

That being said, there is a limited time event going on right now, so this would be a good time to activate it, but two weeks ago there wasn't anything going on, so it would not have been a worthwhile time to activate it.

As of today, I have only used the statue for one week (as an experiment), and don't plan to again unless I find myself behind on these Christmas puzzles. I never specifically went hunting for the Lava Ruby either, it just came to me while I was doing "normal" whacking in the mountains. I did have to hunt the jungle water, of course, but that wasn't hard.

I have been searching for that Ruby for quite some time now and I just can't find it. And with the Christmas event going on I could use the extra mana each day. I am falling behind on puzzles and I would really like to complete them. I don't think there is a secret to it. Once I found it right away. Every other times it has taken me much, much longer. But this is now getting ridiculous. Although I understand an item being rare there really should be some sort of limit the the number of bushes that need whacked in order at acquire of it. Yeesh!

The rare lotus on the Island seems to do the same thing. When it gets ridiculous I let it go for a bit and come back another day.