Hellstone Bar. Hellstone Bars are made from 1 Obsidian and 3 Hellstone at a Hellforge. They are used to create Hellstone Tier items. Items made from Hellstone Bars are the highest quality craftable pre-hardmode items that require bars.
Unitary elastic means that elasticity is equal to 1. In case of price elasticity of demand, e = 1 implies that the percentage change in quantity demanded is equal to the percentage change in price of the commodity. Demand Elasticity is obviously negative. Elasticity = percentage change in quantity demanded / percentagechange in price. Even though perfect real life examples would be tough to list, a close example can be a 1$ increase in price of a good leads to a unit fall in its quantity demanded.
Luxury products are elastic, in comparison to necessity products which are inelastic. Luxury goods are elastic because for a change in price there is a more than proportionate change in quantity. e.g. If the price of a luxury good increases, less people will purchase the good because it is not necessary in their lives - they can do without it.