Amber Shard

The Amber Shard is a DNA shard obtained either through mining or by defeating or catching Pokémon on the 4th floor of Cerulean Cave (access is granted when you beat Kanto E4). 100 Amber Shards can be brought to the Pokémon Lab on Cinnabar Island to revive an Aerodactyl. When defeating or catching Pokémon on F4 of Cerulean Cave, there is a rare chance of the Pokémon dropping a Amber Shard. Don't get too excited about getting a Amber Shard, since it will take you a long time to obtain 100 of them.