Hardstone in Demon's Souls is a resource you need to track down to help upgrade your weapons.
Depending on the stone you want to farm, there are different materials required.
This page will explain where to find Hardstone Shards, Chunk of Hardstone and Pure Hardstone locations.
On this page:
How to get Shard of Hardstone and Large Hardstone Shards in Demon's Souls
For 'regular' Shards of Hardstone and Large Hardstone Shards, the easiest location is from the Filthy Man at the start of Stonefang Tunnel.
He will sell both for souls, and all you need to do is bring the appropriate amount of souls to buy them with.
Weapons which are upgraded with these two Hardstone types are not the best when scaling to stats - but these weapons can be imbued with Magic, and is frankly, the easiest to upgrade to +10. For anything more potent, you need to look at Chunk of Hardstone and Pure Hardstone.
How to get Chunk of Hardstone in Demon's Souls
For the Chunk of Hardstone, you're able to grab them from Crystal Lizards near the Phalanx, Tower Knight, Penetrator and Armor Spider archstones respectively.
In case you're unable to get Hardstone Chunks from Crystal Lizards, you're also able to get them from the Miners in Stonefang Tunnel, or near the Armor Spider Archstone.
This can take a while since the drop rate is quite unforgiving. After that, you'll just need to get a piece of Pure Hardstone, which is easier than it sounds.
How to get Pure Hardstone in Demon's Souls
From the Armor Spider Archstone, make your way to the Crystal Lizard nest. Kill all of the Lizards, which also give you a chance of dropping Pure Hardstone, and then you'll be able to find a piece of Pure Hardstone in this area.
If you are having trouble killing all of the Crystal Lizards in time, we recommend equipping the Thief's Ring and using the Firestorm spell, which will deal massive damage, usually killing the Crystal Lizards in the process.