Iolites are unusual and little known gemstones. They are silicates of aluminum and magnesium.
Their chemical formula is: Mg2Al4Si5O18. Iron can
replace some of the magnesium in the crystal. Because of the range in composition, the hardness of iolates ranges
from 7-7.5 and the density from 2.53 to 2.65 (values for diamond are 10 and 3.52, respectively).
Iolites actually have two colors in every gemstone. One color is the purple-blue similiar to (but bluer than) tanzanite
that is visible from the top of the gemstone. The other color is a pale yellow to grey visible from the sides as
the stone is normally cut.
Legend has it that the Vikings used rough iolite stones to find the direction of the sun on overcast days to allow
them to navigate their boats. Hence the name "Vikings' Compass" for this gemstone. Several other names:
Iolite that means violet; Dichronite that means "two colored"; Water Sapphire for the color; and, Cordierite
after a French geologist.
Last Updated Nov-13-2002