Colours and markings vary between crystals. You are purchasing the Apatite Crystal Egg, pictured.
About Apatite Crystal Egg
Apatite is said to help with weight loss as it can suppress the appetite. If you wanted to use this crystal as an elixir you would need to use the indirect method and not immerse the crystal directly into your water.
Being a Throat Chakra crystal, Apatite facilitates communication and is especially helpful when speaking in public.