The Blue Onyx is an agate Onyx of blue, grey and white layers of fused quartz. Its beauty is sonically unique due to the scarceness of blue stones in nature. The Blue Lace batch was also specially selected because it is the hardest and most rigid among the onyx family, making it an exceptional cartridge housing due to its outstanding sonic qualities. Because of the limited supply of Koetsu's Blue Lace stock, they only issue two Blue Laces a year. A true audiophile statement.