The disadvantage of open pit veins is that the ore is scattered and the collection rate is low.

Now Jia Zhengjin needs more mines to build new buildings!

So he needs a new mine, and preferably a resource-rich underground mine!

The underground mine is relatively dense, the collection rate is also very high, and the efficiency is of course incomparable to that of an open pit mine!

Of course, in the absence of minecarts and minerlights, it is slightly more difficult to mine.

Jia Zhengjin brought a backpack full of materials early in the morning, and then rode the fake dragon on the road alone. Activate the skill of finding ore veins and scout carefully in the area slightly further away from the Holy Dragon City.

Open-pit veins are easy to find, because as soon as you activate the skill, you will see a colorful distribution of various ore veins. But the underground ore veins are a little more difficult, after all, they are all buried deep underground, and even if you open the skill, you may not be able to see it. Some of the things you can see are only very small spots of light, and if you don't pay attention to them, you will miss them.

Fortunately, Jia Zhengjin was lucky, and after spending half a day, he finally found a location full of tiny points of light.

This vein is about eleven kilometers northeast of the Holy Dragon City, which is quite far away!

However, there are no large, ferocious otherworldly animals and demonic beasts nearby, only some relatively docile herbivorous and insectivorous groups exist. You can work here with peace of mind!

The veins were so deep that Jia Zhengjin could barely see dense spots of light the size of sesame seeds when he landed on the ground. Preliminary estimates suggest that it is at least five or six hundred meters above the ground.

Before opening a mine, of course, you must be fully prepared! Moreover, it is impossible for Jia Zhengjin to open a mine by himself, so the materials prepared in his backpack come in handy.

Because of the abundance of minerals, such underground mines are five or six times the sum of all the open-pit veins found by himself before! And Jia Zhengjin also needs to obtain minerals more quickly.

So he directly built a level 1 kobold lair in the clearing, and then built a mine next to the lair.

Immediately after that, 500 kobold miners were recruited from raw meat and stationed in the mines. Recruit another 500 to stay in the nest.

After the recruitment, he immediately asked 1,000 kobold miners to gather in the open space, he took out the virtual backpack and took the iron pickaxe and stone shovel made by 500 kobold craftsmen in the factory one day, fell to the ground to form a hill, and said to the kobold: "Get an iron pickaxe and a stone shovel each, and wait for my order!"

All the kobolds immediately sprang into action and stepped forward to fetch the tool hill. After each got the two tools, he stood in the open space in front of Jia Zhengjin.

Looking at the dense kobold troops in front of him and unable to see the edge at a glance, Jia Zhengjin ordered loudly: "Starting from this area, use a stone shovel and an iron pickaxe to dig down in a stepped manner, and go down to the mining area over there." Line up downward, leaving a gap in between for dozens of kobolds to walk together. Alright, do it now!"

After receiving the order, the kobold miners immediately got busy, lined up in a neat queue and began to dig a pit down. They dig three blocks, then two blocks forward, one block down, and then two blocks forward. And so it repeats infinitely, creating a path to the underground.

Because of the darkness underground, and the lack of lighting equipment such as miners' hats, only some kobolds can only be allowed to carry torches first.

The team doesn't move down very quickly, and it can be expected that it will take quite a bit of time.

Jia Zhengjin simply went to the side and sat under a big tree, closed his eyes and rested.

The kobold miners gathered at an astonishing speed, and with the system's iron pickaxes and stone shovels, the kobold took the lead, quickly digging down the pit, and then began to advance in a stepped slope.

Listening to the tinkling sound in my ears, I watched as the kobolds outside carried the dirt and stones out of the ground one by one, piling them up in the spacious open space on the side. Jia Zhengjin leaned against the trunk of the tree with satisfaction, ready to sleep a little first.

Wait until the kobold digs the path and reaches the vein, and then go down to check the overall situation.

During this time, he was very tired every day, and various things made him have less time to rest. Especially when the elves come to the city, because of the customs, there will inevitably be some small frictions with humans. Just appeasing all parties had already exhausted him. I only have five or six hours left to sleep every day.

Therefore, in a rather sleepy situation, I fell asleep unconsciously.

I was dreaming when I suddenly heard a deafening thunder in my ears, and then I felt the ground tremble a few times!

Jia Zhengjin was instantly awakened, looking left and right with a blank face, "There was an earthquake?"

"Whew~~" The kobold who was not far away from the rocks and dirt outside all shouted at him desperately.

The kobolds were already piled up behind them, and Jia Zhengjin hurried over to put the incredible amount of dirt and stones into the virtual backpack. Then he looked at the kobold miners and asked, "What's the situation?"

"Whoa~" The kobold howled desperately at the mine.

Could it be that something happened below? It can't be some dangerous underground creature, right? Jia Zhengjin was immediately fully armed, holding the golden shield in his hand, and jumped down with the golden spear in his hand: "Illumination!"

Immediately a kobold came down and walked ahead of him with torches.

By the faint light of the torches, Jia Zhengjin moved down the bottomless steps under the leadership of the kobold.

He felt strange, except for the hundreds of kobolds standing outside, there was no movement in those who dug all the way down?

He kept walking downward at an angle, at least for more than a thousand meters, and just when he was almost too tired to do anything, the kobold who led the way in front of him let out a sharp cry: "Whoa~Whoa~"

Jia Zhengjin immediately followed, only to be stunned to find that the steps had reached this point, and there was an incomparably huge pit in front of him.

Could it be that it is naturally formed? Jia Zhengjin approached the past, and felt that the temperature of the nearby soil and stones was quite high. The probe looked down and was dumbfounded!

Inside the huge circular pit with complex shapes, the corpses of kobolds lie all over the place. Every kobold was mutilated, buried in dirt and stones. The scorching breath came to my face, like a furnace. But there was no flame or anything that could generate heat inside.

"Huh?" Jia Zhengjin looked around, studied for a while, and finally found out the reason!

Everything in the crater is like what happened after the Big Bang. And he could faintly smell a special smell. If you think about it, it seems to be biogas! But it was probably the big bang that used up all the biogas, so there was only a little bit of stock left to make a second big bang!

Jia Zhengjin was speechless as he approached the steps of the underground mine! Unexpectedly, these kobolds accidentally dug up a natural biogas vein, so that they could not die and now use torches for lighting, so they triggered a terrifying explosion. The biogas was depleted, five or six hundred kobold miners were all dead, and a huge hole was blown out of the place!