Cobalt blue is an intense saturated blue. It is dense, vibrant and jewel like. The best known sources for cobalt blue sea glass are old vintage Milk Of Magnesia bottles, Vick's Vapor Rub jars, Bromo Seltzer bottles and Noxzema jars. However, there are many other sources for cobalt blue sea glass such as ice water pastry bottle rolling pins, Collyrium soothing eye lotion, glass eye wash cups, Blue Coral auto finish, ink bottles, depression era plates, bowls, cruets, cake stands, decorative baskets, tumblers, drinking glasses, dessert dishes, egg cups, vases, candle holders, candy dishes, perfume bottles and other glass bottles that held medicines, poisons or castor oil.
In Puerto Rico, and possibly elsewhere, LAXOL castor oil bottles are a source for cobalt blue sea glass. We found the LAXOL bottle pictured below while hiking along a stream in Rincon, Puerto Rico that empties out into the sea. It is embossed with LAXOL and A.J. WHITE LTD NEW YORK RIO DE JANEIRO.