American Fire Glass AFF-COBL-10-J 1/4" Cobalt Blue Fire Glass 10 lbs Jar. Cobalt glassware was the signature product of artisans during the middle ages. Even today, the color retains its old world charm and is very popular among designers. If your customers are fond of this striking tone of blue, we offer cobalt fire glass from our 1/4 inch fire glass collection. Perfect for homes with traditional décor dominated by shades of blue and earthen tones, this 1/4” cobalt fire glass is sure to spice up the ambiance and please the eye. It can turn even a drab fireplace or fire pit into a work of art. When set alight, the flames rising from the bed of 1/4” cobalt fire glass will create a fire display that will leave the audience completely in awe.