They have been found in ruins dating several thousand years. They are valued as gifts symbolizing love. There are many ways that dealers treat gemstones. The savvy buyer asks lots of questions and hopefully tests the results. This treatment brings out color and removes imperfections.
Many dealers know if the stones they are selling have been irradiated.
Honest ones will tell you if they are aware of the treatment. This is the most common treatment used. On clear stones, dye may be visible in cracks that are darker than the rest of the stone. Sometimes dye appears as a residue that rubs off or white patches. Lapis and Rose Quartz are commonly dyed.