The price changes daily. To find out what the price is go to the home page click "game guide" on the top bar and on the drop down list click grand exchange and the search adamant pickax. The current price as of March 30 2010 the price is 1,810 gold pieces. Hope this helps!
Grand Exchange
Rune Pickaxe - 18,145gp - 20,055gp
Bronze pickaxe - 181 coins Iron pickaxe - 108 coins Steel pickaxe - 948 coins Mithril pickaxe - 478 coins Adamant pickaxe - 1468 coins Rune pickaxe - 18761 coins Dragon (m) - 16.3 Million Coins
The adamant battle axe and adamant scimitar are.
All adamant armour like Adamant full helm, Adamant platebody, Adamant plateleg
You can buy a Mithril Pickaxe from Nurmof's Pickaxe Shop in the Dwarven Mine, but beware of the much more expensive price offered by the shop. You can also buy it off of the Grand Exchange for the best price in RuneScape shops. It's also possible to obtain a Mithril Pickaxe from monster drops from Living Rock Protectors, Dagannoth Rex, and Living Rock Strikers.
Adamant Dragons do not exist. The highest-tier metal dragon is still Mithril.
It is hard to give exact numbers - the increase in speed probably depends on the mineral you mine, and on your mining level. In any case, it is best to use the most advanced pickaxe you can - unless you have trouble affording it.
Full adamant cost around 17-20k in ge and requires 30 defence.
A volatile pickaxe is a kind of pickaxe in runescape.
addy scimitar
The next level would be rune armor.