Here are the 3 Jasper Spellstone cards added to the Druid class from the Kobolds and Catacombs expansion.
You upgrade the card when you gain 3 armor giving you better value for the mana cost each time.
They then do the following damage:
Lesser Jasper Spellstone – 2 Damage to a minion
Jasper Spellstone – 4 Damage to a minion
Greater Jasper Spellstone – 6 Damage to a minion