This guide ( sorry it is not a video ) will show you how to farm Rich Thorium Veins and skill up your mining even faster and/or earn some gold in the process.
To do this faster you need to be higher level ( 70+ is best ) and to have mining skill at lvl275 ( since on that level you can start to mine Rich Thorium Veins ).
Now the pictures
Picture 1.
You will start here, this is the 1st place you'll see when u enter DM east.
So go right and forward.
Picture 2.
Jump down ( walk off the ledge ). Look on mini map where i did so u dont confuse.
Picture 3.
Go to that doorway ( look again on mini map where it is ), and turn left when you are inside.
Picture 4.
Go straight until you see another doorway.
Picture 5.
Enter that doorway and go to the top. You will see a boss u need to kill. So kill it
Picture 6.
When he is dead, go back to that big open area, and you will see big NPC. Talk to him ( you cant talk to him before that boss is dead ).
Picture 7.
Follow that path and that NPC will destroy the door for you. Go trough then and corridor.
Picture 8.
When you get out of corridor you'll find yourself in a big open space. Go to the center of it and kill the boss. ( just dont kill him to fast since he can bug ).
Picture 9.
When you kill him and adds he spawns go through cave entrance that will now be behind him. And here are your Rich Thorium Veins. Now all you need to do is go through that cave and exit the instance. The entire "trip" took me less then 7min.
Reset and repeat.
I found that this is the fastest way to level up mining from 275-300 since you'll get skill point for each vain you mine, and there are always 2-4 rich thorium veins.
From each run you can get from 9 to 20 thorium ore + some gems. On my server stack of thorium ore sells for 50-60g. So its not bad to earn some gold while you level mining.
P.S. sorry if it is a repost. Was looking but couldn't find it...