The Mystery and Allure of Cobalt Sea Glass

Updated from version published in spring 2014 edition of Shorelines Newsletter 

Ellie Z. Mercier

 

Sea glass collectors can certainly relate to the jubilant sensation that transpires when striking gold. Of course, not the sought after nuggets that lured settlers west during the Gold Rush of 1849, yet smoothly tumbled specimens of the finest quality, which actually have no resemblance to gold whatsoever but are dressed in the magnificently rich hue of cobalt blue.

Many enthusiasts would likely agree that discovering prized shards of ruby red, yellow, and purple – and especially those boasting coats of orange – are surely hobby-related milestones worth writing home about. However, although true blue finds are generally more plentiful than the shades ranked as most scarce, few collectors can resist the mysterious allure of cobalt blue sea glass.

Detecting glimpses of well-worn cornflower or royal blue gems ashore may generate well-deserved shrieks of delight on behalf of some beachcombers, while others may experience a stunned silence. Yet despite the differing external reactions to such feats, collectors are often left to ponder the magical significance of the cherished shade.

Represented as the first element in the ninth column of the periodic table, cobalt possesses an atomic number of 27 and is recognized by the symbol Co. The mineral was formally discovered in 1735 by Swedish chemist George Brand, who dispelled the myth that the element Bismuth was responsible for the rich blue color of glass. However, coba

lt compounds were used for thousands of years before Brand isolated the element. Scientists have traced the use of cobalt back to the ruins of the ancient city of Pompeii and to early civilizations of Ancient China, and the mineral was also used in Egyptian art and Persian pottery. Although prior to the 1940s, cobalt was used sparingly due to the limited quantity, the expense, and the difficulty to extract the mineral. Modern day collectors often associate the shade with luminous blue medicine bottles and cosmetic jars produced during the early to mid-twentieth century.

However, cobalt’s use as a coloring agent is not limited to glass, jewelry and ceramics; the compound is also used as a pigment for paint, ink and even cosmetics. Other applications of cobalt include the production of rechargeable batteries and the electroplating of cutlery and jewelry. Rather than an element found in nature, cobalt is a hard yet brittle mineral contained in the Earth’s crust and is a byproduct of the mining of other metals, including nickel, copper, silver, lead and iron. In its natural state, the color is a bluish-white shade, similar to gray. Cobalt salts are actually the source of the brilliant and permanent rich hue associated with the mineral. The majority of cobalt is mined in Africa, particularly in the Democratic Republic of Congo (or Zaire, prior to 1997), which extracts close to forty-percent of the world’s supply annually. Other sources are found in Canada, Brazil, Russia, China and Morocco. Also, researchers believe there is a vast source of cobalt contained in the ocean’s floor, although scientists currently lack the technology to extract the element. Interestingly, studies conducted by the United States Geological Survey conclude that cobalt likely exists in the shallow waters of the Hawaiian Islands (USGS).

Ironically, among the many interesting facts about cobalt is the mysterious nature of how the color’s name originated. Long ago, superstitious German silver miners believed that malicious spirits were affecting their health as well as stealing silver ore from the mines, and they referred to these spirits as kobalt, a derivative of kobold, which is German for goblin. Other fascinating facts surrounding the element include artist John Varley’s presumption that cobalt is an ideal substitution for the shade of ultramarine blue, which was widely used for painting skies. Another artist, Maxfield Parrish, was so well known for his superior cobalt blue sky-scape paintings that the hue is sometimes referred to as Parrish blue. Cobalt was also the primary pigment used in notable blue and white Chinese porcelain, originally produced in the late eighth or ninth century. Furthermore, cobalt is used to illuminate the cornea of the eye to detect corneal scratches and is used in the production of magnets, and Radioactive Cobalt is used to treat cancer. And oddly enough, cobalt is added to the diet of sheep in order to prevent disease and improve the quality of their wool.

The outward reactions of those fortunate enough to experience such a hobby-related milestone as striking gold – or rather, witness sudden brilliant glimpses of blue jump out from the sandy canvases before them – may differ significantly, but few sea glass collectors can resist the powerful allure of cobalt treasures, which in many aspects, are truly gifts of Mother Nature.

Photos: Ellie Mercier

  • Ellie found the frosty marble in the Abacos (her first marble find & she remembers that she was extra excited because Richard LaMotte shared that cobalt marbles are more rare than red marbles).
  • The bottle is from Ellie’s bottle collection – She also collects antique bottles.
  • Ellie found the jar lid in the Chesapeake Bay (almost a decade ago)
  • Yet most interesting is the image of the large cobalt shards, which Ellie found following the 2009 festival in Lake Erie…One of her customers took me combing along the river in nearby Conneaut, Ohio, where much slag glass was discarded in the 1960s by the GE Light Bulb Base Plant (these are huge, and the hue is extremely vibrant, alike bright violet).

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