Iron is by mass the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust. Pure iron is relatively soft, but is unobtainable by smelting. The material is significantly hardened and strengthened by impurities, in particular carbon, from the smelting process. A certain proportion of carbon (between 0.002% and 2.1%) produces steel, which may be up to 1000 times harder than pure iron.
Resin is a durable and transparent plastic that is especially suited for jewelry-making because of its ease of use. It begins in a liquid form, but after being casted, becomes quite durable. Special resin molds with smooth surfaces are created to give it a glossy finish.