Elemental ore is an ore that may only be obtained by killing a level 35 earth elemental after trying to mine the elemental rock. This ore can only be obtained during and after the Elemental Workshop I quest, and turned into elemental metals. Elemental ore is only found in the Elemental Workshop dungeon beneath the Seers' Village, in the house with the anvil, next to the bank. Earth elementals are found in the western area on the first level of the workshop.
The second level is to make bars, and repairs are needed here too. One elemental ore and four coal may be smelted into a bar of elemental metal using the blast furnace in the southern area of the Elemental Workshop (level 20 Smithing is required). This bar is used to smith the elemental shield and helmet.
At level 30 Smithing, the elemental metal may be primed and turned into a primed elemental bar. This may be used to create the mind shield and mind helmet in the Elemental Workshop II quest. If players try to use Superheat Item on the ore, a message appears that says "Even this spell is not hot enough to heat this item". Also, if a player tries to use any other furnace besides the one in the Elemental Workshop, a message appears that says "This furnace is not hot enough to smelt elemental ore".
For an exhaustive list of all known sources for this item, see here
Note: The ore is only dropped from the elementals that appear when you attempt to mine elemental rocks.