The Frag Mine looks like a tan shaped disk with a black gear and red button on top. The tan paint is most likely used to camouflage the mine out in the desert covered Capital Wasteland. The Frag Mine will begin beeping when a target comes within a short distance to it until it is disarmed or it detonates. The time until detonation depends on the Explosives skill of the person setting it off.
To use a land mine you equip it like any other weapon, then use the fire button (dependant upon what platform, PC, Xbox 360, etc...) to arm it and drop it on the ground. To collect a hostile land mine you have to approach it then use the "activate" button (E on the PC) on it once to disarm it and then again to pick it up off the ground. This can be risky, especially at low levels of Explosives skill. There appears to be a quirk in the programming so that the mine will detonate based on how close you are to it's center regardless of the Z axis (ie up and down) while the distance you have to be to "activate"/disarm it does take the Z axis into account. This means that going downhill or down a set of stairs the landmine will often explode before you're able to get close enough disarm it. Your best bet is to crouch and, if you can, approach from the down hill side so that you're closer to the mine's level on the Z axis. Aiming your crosshair at the mine, glide towards it clicking the activate button as quickly as you can. By switching to a walk instead of running you're also less likely to overshoot the mine and fail to disarm it.
Like a Frag Grenade frag mines have a relatively small blast radius and will do damage (from a maximum at point blank range of about 65 at skill level 25 up to 100 at a skill of 100) to any friendly or enemy target (including yourself) within that radius. The further away from the center of the blast the less damage that is done. Mines can also detonate each other if they're set too close together. This can work for you when you're trying to take down a particularly tough opponent by hitting it with several blasts at once. However if you aren't careful in how you lay the mines the first might set off the others before the intended victim is within range of them all (ie if you get lazy or rushed and just drop a straight string of them as you're backing away from an oncoming opponent).
If you're trying to ambush a victim that moves along a pre-determined patrol path you can lay a simple string of three or, at most, four straight across (not along) that path. More than that in a straight line and a lot of blast radius will be wasted. If you're feeling ambitious you could even try for a U shaped pattern with the open mouth towards the direction the victim will be coming from so that, when they reach the mine at the base of the U, they'll be surrounded on three sides by the blast. Not many creatures other than a Behemoth (mutant) or possibly a higher level deathclaw is going to need that much damage though.
If you're up against an opponent that doesn't have a fixed patrol path you can lay your mines at a doorway or beside an obstacle like a pile of rocks then fire a weapon to attract your victims attention before ducking back so that they chase you and run onto the mines. Just remember to run well back so you don't get caught in the blast.
If you get caught by surprise by a tough opponent like a giant radscorpion you can try running away from it and dropping mines as you go. Don't try this if the victim is already close to you or you could get caught in the blast radius when the mine detonates. Also be careful not to drop the mines too close together as you run or the chain reaction when the first detonates could set off the one right under your own feet. This method works particularly well if you can cripple the victim's legs with a Dart Gun to slow it down.
You should be aware that some creatures that fly/hover like the Mr. Handy and Mr. Gutsy robots won't detonate land mines themselves (technically, they aren't stepping on them) but will be damaged by the blast from one. If you can manage it, lure them over the landmines then shoot the landmines to detonate them (this can be a little tricky at first) or simply use a grenade in VATS to attack the victim and detonate the landmines at the same time.
Like hand grenades mines can be "reverse pickpocketed" onto a victim where they will arm and detonate on their own. You have to be able to stealth in close enough behind the victim to "activate" them then simply move a bomb from your own inventory to theirs. Unless you have a particularly tough opponent this is usually a guaranteed kill. Note that "vital" NPC's can't be killed in this manner. (tested on 360)
Frag mines are useful weapons against a Mirelurk. These creatures have very tough armour but very low hitpoints. You can find yourself wasting a lot of ammo trying to kill them. A Mirelurk will move very slowly towards you, since it only ever attacks with melee. Just drop a frag mine and retreat. It takes 3 frag mines to kill a Mirelurk.
When you plant a frag mine, you can walk over it and it will not explode. If the frag mine is not needed, then you can simply walk over to it, disarm it, and pick it up again so it does not go to waste.
If you equip frag mines, drop about 10 of them, and pick them back up, your inventory will show two sets of frag mines, both equipped. If you then take out a melee weapon, it will show up as a frag mine, and you can hit enemies with it. This is a very humorous glitch, as using a Shishkebab will look as if you are lighting them on fire. With a frag mine.(Confirmed on 360)
- Frag mines are easy to see in darkness, due to their glowing red "armed" light.
- Once you've spotted a mine, it's arguably better to run up to disarm it, than to creep up on it. This is because the detect radius doesn't always seem to be the same as the disarm radius - and if you move slow, you may start its countdown while you still can't reach it.
- Beware of uneven terrain and especially things jutting up, like the steel re bar sticking up in the ruined building that Arkansas inhabits in Minefield. It can block your reach, even when very close. Approach mines from an angle that has no protrusions in the way. You can also use hostile mines as weapons because when you disarm it, it becomes friendly.
- The effectiveness of your mines may be affected by your enemy's explosives skill. Though rare, some enemies are able to walk past the mines and suffer less damage (Eulogy Jones is an example). When Eulogy approaches the mine, the player can hear the usual beeping, but it is much slower than normal -- similar to the effect a player gets when trying to disarm a mine with high explosive skill. Note that this may in fact be a bug and can be proven/disproved if tested using an NPC with known explosive skills (Charon).
- Frag mines look very similar to a scaled-down version of the real-life, Russian TM-46 anti-tank mine, the most notable differences between the Frag mine and TM-46 being the addition of the light, the replacement of the pressure fuse with an apparent proximity fuse as well as the removal of the secondary fuse on the side of the mine near the carrying handle.
- Frag mines, like all explosion types, will cause grenades within the blast radius to also explode.