also what is the difference between the 2 substances that account for the noted difference?
Quartz is volcanic lava that has cooled over thousands of years and become solid. It's chemical name is Silicon Dioxide and is used to make Silicon Chips. If you take a 'chip' off of Silicon you end up with a Silicon Chip. During the formation of a Quartz Crystal (as lava is hardening to form a crystal) if there is Iron in the area it will make it turn purple and then it is known as Amethyst which is another semi Precious stone. I'm from UK so if your not then try searching the internet but here you can buy them from holiday areas such as Hastings, Southend etc as well as new age shops. I'm not sure what you want it for but there is no scientific proof whatsoever that Quartz Crystals aid healing or meditation or anything like that.
