LESSON XIII
COLOR—Continued
BLUE STONES
The species that furnish blue stones in sufficient number to deserve consideration are, aside from opaque stones:
1. Corundum (sapphire).
2. Spinel.
3. Tourmaline.
4. Topaz.
The species that furnish blue stones in sufficient number to deserve consideration are, aside from opaque stones:
1. Corundum (sapphire).
2. Spinel.
3. Tourmaline.
4. Topaz.