I had the same brand from a different supplier.Particle size was 3-6 mmHi Kempster,
Sorry to hear about your bad experience. Here's the link to akadama I bought, it's really good quality 🙂
http://m.ebay.co.uk/itm/262202695000
Just as a warning, it's best to sieve and get rid of the biggest "granules". It will make planting easier. And also, rinsing is more important than soaking. It takes a while to get rid of the dust... And don't worry if the water is getting slightly cloudy when flooding the tank, it clears very quickly.
Cheers,
Manu
http://www.yorkbonsai.co.uk/akadama-bonsai-soil-14-litres-i78.html
It is really good