fluorite

https://crystal-cure.com/flourite.html :
Formerly called fluorspar, fluorite has a wide range of colors including yellow, blue, pink purple and green. It is an interesting and beautiful stone because often more than one color occurs in a single stone. The ancient Egyptians used flourite to carve statues and scarabs, the Chinese have used it in carvings for over 300 years.
Fluorite is said to absorb and neutralize negative vibrations. It makes one more receptive to the vibrations of other stones.
Fluorite is known as the "Genius Stone".

• increases concentration
• helps in decision-making

Fluorite may be used with other stones. It helps to open the way for the power of other stones to be effective. It can be used as a meditation stone to help energize the body and raise the power of concentration.
Locations where fluorite is found include Canada, USA, South Africa, Thailand, Peru, Mexico, China, Poland, Hungary, Czechoslovakia, Norway, England, and Germany.