I bought a set of 11.5 gram chips like the ones you are describing off ebay, And quickly resold them. They to me did not feel like there was any clay in them whatsoever. To me they felt like 100% plastic? I ended up buying 2-500 piece sets from an internet site called www.oneeyedjacksgaming.com. the chips are 8.5 gram but, quality they feel like Bud jones Chips. I own a screen printing shop in San Diego so I printed them myself with my name and denominations.

Andy