There are many crystals which help to clear open and align the chakras. Kyanite is a good one. Amethyst is good third eye one. Tanzanite and chariote connect the heart and the third eye. For third eye I suggest either acquiring or visualizing amethyst. Azurite is a good one for the throat third eye and crown.
Focus on the area between the eye brows. Balance this with focusing on the tip of the nose at different times. You can also look up through the center of the forehead, or look and focus on the center of the nose.
amethyst
this is a very good one for all chakras called fluorite
Tanzanite a very good one for connecting the third eye with the hear to prevent the mind from going off on tangents and guess also to prevent the heart from being blind.
and of course kyanite a very good one as it is cleansing and aligns all the chakras.
and to balance out the amethyst my favorite heart chakra stone dioptase
The beauty of this stone does not translate into a picture so well. I have one and it is my most favorite stone in my whole collection.