Red sandstone

Red sandstone is the ingredient used to create robust glass after As a First Resort.... It requires 81 Mining to obtain; this requirement is boostable. Until 21 January 2013 the only location to mine red sandstone was outside Oo'glog, but with the Desert task update it is now possible to mine some more in a rocks outside of Sophanem after completing the elite Tasks. Mining this yields 70 experience per block, but players are only able to mine a maximum of 50 red sandstone per day, which resets at midnight GMT. Plus a possible additional 25 near Sophanem.

Obsidian golems mining boost does NOT work for this.

Note that even though only 75 can be mined per day, there is no limit to the amount of robust glass that can be created per day. There is no level requirement to make robust glass.

Uncut gems and strange rocks can be received from mining red sandstone. In addition, both the penance horn and the sacred clay pickaxe will give bonus experience when mining it, as does the mining ring from clan citadels. However there is currently a bug where using the mining ring will drain charges from the ring but not give you the additional experience.

According to Rutmir Arnhold, the walls of Oo'glog are composed of red sandstone, but the ogresses won't let anyone mine them for obvious reasons.

Shooting Star
It is possible to mine more than the maximum daily amount with the reward from shooting stars, which gives the player a chance of receiving double ore. Assuming the player is mining all the red sandstone available, the effect of the reward given by the shooting stars will allow the player to mine up to about 34 extra pieces per day. However, the extra-ore effect of Varrock armour does not allow you to mine multiple pieces of red sandstone.

Resourceful aura
The Resourceful aura can also be used to slow the depletion of the rock so that more than 50 (75 if the Desert elite tasks have been completed) can be obtained per day.

Trivia

 * Red sandstone alludes to the parallels Oo'glog has with the Australian outback. Most rocks tend to be red and difficult to mine in large amounts.
 * Red sandstone is gathered at almost the same speed as concentrated gold ore.
 * Drinking a dose of juju mining potion will automatically bank the red sandstone for you.
 * Beasts of burden can hold red sandstone even though it is untradeable. This is the only known item besides untradeable potions in vials or flasks for which this is the case.
 * When red sandstone was first introduced into the game, emptying the deposit gave players a message in their chatboxes reading, "You empty the rock of sandstone. There will be some more tommorrow," with "tomorrow" spelled incorrectly. This has since been fixed.
 * On the day of release, red sandstone was tradeable, but this was changed by an update to prevent an excessive influx and a decrease in prices for flasks.
 * Unlike the animation for mining concentrated ore, which continues as if no ore was mined until the player's inventory is full or the deposit is emptied, the animation for red sandstone restarts after each successful attempt.
 * On 7 September 2012, the rock from which you mine was moved a few squares south.