Cor Lapis is a crystal in Genshin impact that is scattered around the Liyue nation, and can also be bought at Liyue Harbor.
It is a relatively common mineral that is usually located under cliffs or caves. The most common place to find it is on Mt. Hulao.
Cor Lapis comes in a form of yellow mineral that has to be destroyed to be obtained.
A tip for mining Cor Lapis and other sources is to use heavy sword characters. Characters such as Noelle and Beidou are characters who has huge swords compared to Qiqi or ranged characters such as Amber. These swords allow Cor Lapis to be destructed quicker with three to four hits.
If you are on a hunt for Cor Lapis, you might want to refer to this video. This video provides four efficient routine to farm Cor Lapis on the map in the shortest amount of time.
Where to Find Cor Lapis in Genshin Impact
Another way to obtain Cor Lapis is to buy it at Liyue Harbor.
Changshun is a merchant standing next to the Jewelry Shop. She sells Cor Lapis for 1500 per item and you can buy five per two days. The price is not bad, but she does not sell a lot. You probably don't have to worry because Cor Lapis is relatively easy to find.