How do you get thunderstone in Pokemon Silver?

Answer 1

Before Elite Four:

From Ecruteak City, go left then talk to a girl (pretty sure it's Lass Dana) and she will challenge you to a battle. After, she will give you her phone number. Wait for her call then if she has the Thunderstone she will give you one.

After Elite Four:

Go to Cerulean City. If you have played through Red, Blue or Yellow, then you should know where Bill's house is. Bill's grandpa will be in his house. Talk to him and he will ask you a few riddles. To answer the riddle figure out which Pokemon he's talking about and show it to him. He'll give you a stone depending on which Pokemon you give him.

1. Lickitung - Everstone

2. Oddish - Leaf Stone

3. Staryu - Water Stone

4. Vulpix - Fire Stone

5. Pichu - THUNDERSTONE

And there you have it. A Thunderstone.