There may be as many as 2 million of these included crystals per square centimeter, scattered uniformly through the quartz. Light entering the quartz is scattered by these tiny particles, the scattering being most pronounced for blue light. The light reflected back to the eye is blue. This effect is also responsible for the blue color of the sky. This is what occurs in the sky at sunset.
Titanium is also responsible for the color of rose quartz.
In this form, the titanium absorbs all colors except the rosy pink one we all know so well. Artificial blue quartz can be made by including cobalt impurities in quartz grown in the laboratory. Natural blue quartz can rarely be used for lapidary purposes, but it is wonderful experience to find it and see what looks like pieces of the clear blue sky embedded in the solid rock.