There is no mossy rock in HeartGold. There is not one in SoulSilver, either. A mossy rock is only found in Pokemon Diamond and Pearl. You must trade for a Leafeon to get one in Pokemon HeartGold.
If you are talking about Diamond/Pearl/Platinum, then the mossy rock is in Eterna Forest.
some mysterious rock that evolves eevee.
level up an eevee in Eterna forest by the mossy rock by the first entrance to the forest.
in the slowpoke well and there going to be school kid
You catch it in Eterna Forest, not far south of the mossy rock. It's a little harder to find than other pokemon. Try it with a poke radar.
use a mossy rock. wonder mail code: =2X3S36X4=%9 RTWHFN69+@F=
You can't take the mossy rock. It's there for evolving an eevee into a leafion. What you have to do to evolve it is to level him up around the mossy rock then he will evolve.
some mysterious rock that evolves eevee.
Mossy Rock cannot be brought in Pokemon Platinium as they do not exist as a item. You need to visit Eterna Forest in order to find the Mossy Rock to evolve Eevee.
the mossy rock in pinwheel forest
The mossy rock is in Pinwheel forest. The only thing you need to do is to level up your Eevee whithin Pinwheel Forest to evolve it.
They are in the Safari Zone
Pallet town
you get it AFTER you beat blue
There is it is in ilex forest
there's no moss rock in heartgold/soulsilver. To get it you need to trade from a different game. Sorry!
There is no mossy Rock in Ilex Forest. The only Mossy Rocks are in Pearl/Diamond/ Platinum/Black/White
Possibly in the forest