I’m probably wrong but possibly this.
Another accessory mineral, cordierite is found in high-magnesium, high-grade metamorphic rocks like hornfels and gneiss. Cordierite forms grains that display a shifting blue-to-gray color as you turn it. This unusual feature is called dichroism. If that isn't enough to identify it, cordierite is commonly associated with mica minerals or chlorite, its alteration products. Cordierite has few industrial uses.
Glassy luster; hardness of 7 to 7.5.
Dumortierite
This uncommon boron silicate occurs as fibrous masses in pegmatites, in gneisses and schists, and as needles embedded in knots of quartz in metamorphic rocks. Its color ranges from light blue to violet. Dumortierite is sometimes used in the production of high-quality porcelain.
Glassy to pearly luster; hardness of 7.
Glaucophane
Graeme Churchard/Flickr/CC BY 2.0
This amphibole mineral most often is what makes blueschists blue, although bluish lawsonite and kyanite may also occur with it. It is widespread in metamorphosed basalts, usually in felted masses of tiny needle-like crystals. Its color ranges from pale gray-blue to indigo.
Pearly to silky luster; hardness of 6 to 6.5.
