Coal

Coal is a resource that can be obtained through mining coal rocks or concentrated coal rocks in various places around RuneScape. It is one of the most important mined materials in RuneScape.

Coal can be mined with a pickaxe by players with a Mining level of 30 or higher, granting 50 Mining experience. Players can, however, mine it at a faster rate the higher their Mining level. After being mined, a coal rock takes an average of 42 seconds to respawn. 81 pieces of coal can be stored into one inventory space by using a coal bag, obtained from Dungeoneering for 4,000 dungeoneering tokens. Coal can also be obtained by having the subjects of Miscellania gather it. In order to gain coal, players must put a number of coins in the coffers and set the subjects so that they will be mining. They will automatically mine coal and a few gems. Its noted form is a possible reward from Temple Trekking and can sometimes be found inside barrels.

With a Divination level of at least 29, 3 iron ore may be transmuted into 1 coal. This costs 2 bright energy and yields 6 Divination experience.

Coal is needed to make elemental, steel, mithril, adamant, and rune bars.

Value
The market price of coal was previously stable at around 170 coins each, but rose gradually to over 300 coins in the middle of 2010. Since then, its price has declined slightly to about 250 coins. After free trade was reinstated on 1 February 2011, the price briefly fell to about 160 coins. However, due to an increasing amount of bots and the fact that the speed of gathering ores is largely dependent on the amount of players fighting over rocks, the competition over rocks caused the bots to decrease mining efficiency among themselves and legitimate players, causing the price to rise dramatically. During the Invasion of Falador, there was double experience at the Artisans Workshop. This caused the price to rise to around 500 coins. It's currently at coins. Iron ore is mined at a faster rate and has a price difference of to coal, so many players prefer to mine that instead.

Respawn rate
Coal, like all other mined rocks, respawns at a rate directly proportional to the number of people in the rock's RuneScape world. If the world is empty, the rock respawns in 1 minute; if it is full (with 2000 players), it respawns in 30 seconds. Thus the respawn rate of coal is
 * $$60-\frac{3x}{200}$$ seconds,

where x is the number of players in the world.

A table of respawn rates is given below.

Trivia

 * In the game, mining coal gives a higher chance of receiving gems than other mining spots. In real life it is the same, as coal beds can usually supply the needed pressure and carbon for gems to form.
 * Another way to obtain coal is to explore for treasure using dwarven squads during a Mobilising Armies round. Players can also get it as a spoil of war.
 * Coal is not an ore; ore requires extraction to obtain the element, whereas coal is found in its usable form.
 * As a joke around Christmas time, some players give coal to other players saying it's because they have been very naughty this year, e.g. killing innocent guards, picking people's pockets, etc. This was turned on its head during the 2009 Christmas event, where the naughty NPC Tiny Thom was delighted to have been given a lump of coal due to its market value.
 * Coal rocks in the Keldagrim north-east mine have not been updated, and are completely black, rather than brown or grey with black veins.
 * It's possible for two players to receive coal if they are mining it at the same time.
 * The examine text states "Hmm a non-renewable energy source!", a joke on coal in real life as it cannot be replenished once extracted.

Coal Coal Coal