Orundum
Orundum is a currency in Arknights.
Made from Originite Prime, it also contains other minerals. In the past, it was used only as a conductive element, but it has since become a store of credit value.
Usage
Extracted and processed from Originite Prime, Orundum is used both as a conductor for electronics and Originium Arts as well as a valuable mineral akin to that of gold and silver.
Orundum is used for headhunting. A single pull costs 600 
while ten consecutive pulls cost 6000 .
Acquisition
Other than the methods listed below, Orundum are often given out during events and as form of compensations, typically for maintenance; the latter of which is through the in-game mail.
Originite Prime
1 
can be traded for 180 .
Operations
Annihilation operations award Orundum when cleared, with the amount depends on the number of enemies defeated.
There is a limit on how much Orundum the player can earn from Annihilation operations in a week; initially the limit is set to 1200 , and clearing Lungmen Outskirts and Lungmen Downtown increases this limit as part of its one-time rewards up to 1600 and 1700 , respectively.
From the introduction of the Annihilation Rotation system, the cap can be increased to 1800 by completing missions that requires the player to reach a certain amount of kills in a single run of the Rotating Mission operation. Note that the missions' progresses will not be reset when the Rotating Mission changes.
Paradox Simulation operations award 200 when cleared for the first time.
Missions
The player can earn 100 in each day from Daily Missions and 500 in each week from Weekly Missions, for a total of 1200 per week.
Store
Up to 6 stocks of 100 (for a total of 600 ) are available for purchase in the first tier of the Commendations Store for 40 
each. In the third tier, an unlimited stock of 100 can be purchased for 50 each.
The player will receive 200 every day (as part of the daily reward) when the Monthly Card is active. Over the course of 30 days, this amounts to 6000 (or 10 pulls). The 6 from the Monthly Card is equal to 1080
Pro Enhancement Packs include Orundum equal to the amount received for converting Originite Primes used to buy them.
Trading Post
Originium Shard can be traded for Orundum in Level 3 Trading Posts by completing Orundum trade orders which is available once said Trading Post's business strategy is changed to Orundum trade with Rim Billiton. Each Orundum trade order takes (baseline) 2:00:00 to exchange 2 Originium Shards for 20 .
Tips
- Assuming that the player completes all daily and weekly missions, and maxes out their weekly Orundum limit from Annihilation operations, one can earn 6000 in 2 weeks, which is enough for ten headhunting pulls.
- Unless the player no longer has any use for
LMD and materials, it is ill-advised to get Orundum through Originium Shard production and trading due to the 
Sanity costs being not worth the reward.
Trivia
- According to Arknights CN's 2nd Anniversary livestream, a grand total of 4,901,491,600 had been acquired by trading Originium Shards at Trading Posts.