The rule of thumb when dealing with Ordonite (or Vile) enemies is simple:
Bring Splash damage.
- Give preference to splash sources that can cover a lot of ground or have very high radius.
Suggested Gear
This SMG has natural piercing, and each projectile has a chance to cause an explosion on hit, even after they've pierced a target and hit the next.
- This is as close as it gets to literal perfection against The Stone Demon when talking about 'normal', shooting gun. The crystals are lined up on its back, making them a prime target for the piercing effect + explosions of the
Darkbeast. - A Ripper (Charge Mag) version is excellent for boss encounters.
The Airstrike underbarrel, which can roll on Epic
Torgue AR or even
Potato Thrower IV, can simply demolish the Ordonite crystals. You'll want to pair it with:
- Head Ringer
Torgue Enhancement, which provides 100% Splash Radius.
With as many radius boosts as you can get on your Enhancement, this can be a respectable choice to deal with the Ordonite crystals.
- Head Ringer
Torgue Enhancement, which provides 100% Splash Radius, and can roll further radius boosts on its passives.
The infamous Spread Launcher is, unsurprisingly, very good at this too.
- While it may not always deal with all crystals at once, you can always bring a second or even third Spread Launcher to completely bypass its cooldown.
- If you have a Torgue (Impact Mag) part on your Spread Launcher Jakobs (Loader Mag), you can pair it with a Head Ringer
Torgue Enhancement for massively increased explosion radius. - AMP Synergized and Amp (Amplified) Repkits are very useful for Spread Launcher tactics.
Ordnance players looking for a solution can find it here. Pair an Incendiary Hailspike with Tier 3
High Caliber and you'll be good to go.
Licensed Weapons + Enhancements Torgue (Impact Mag) 
Pair any Torgue (Impact Mag) weapon with an Air Burst
Torgue Enhancement, and you don't even have to directly hit the Ordonite crystals anymore, since Air Burst detonates automatically when near the hitboxes.
- This can be really helpful for dealing with the tail crystal.
- The
Pumper Enhancement can not only give you the Air Burst auto-detonation, but also massively increased radius coming from the Head Ringer effect. A perfect combination.