While we're on the subject of substitute stones, be aware of a few things that I have learned in the midst of my becoming familiar with semiprecious-stone jewelry-making supplies. Be cognizant of what you are investing in if you want to buy the following things. So if you are purchasing these stones, do it from a trustworthy dealer who identifies any stones that have been dyed, heated, stabilized, etc.
- Turquoise. Most natural Turquoise is too soft to make jewelry with, in the natural state it's in when it's mined. So you will encounter a lot of Turquoise that has been stabilized with resin or other materials. There is also a lot of imitation Turquoise out there, such as dyed Howlite or Magnesite; or some imiitation Turquoise is made of entirely synthetic materials.
- Hematite. Natural Hematite can have a reddish coating on it -- as this is the mineral form of Iron Oxide (rust), that's not surprising. So if you see that, you are likely to be getting the Real Deal. But there is A LOT of manmade Hematite out there. Magnetic Hematite is one such stone; two others have the trade names Hemalyke and Hematine. Again, a reputable dealer will identify their stones as such, if they are a manmade version of Hematite.
- Onyx. I was surprised to find out that a lot of black Onyx is actually dyed that color (though it does occur in black naturally, as well). If you dislike using color-enhanced stones, then checking up on the history of the Onyx you're considering buying will be beneficial.
- Citrine. There is a lot of "citrine" that has been created by heating Amethyst, a more common version of Quartz. If you do some googling and look at images of heated-Amethyst versions of Citrine, it will help you ID it when you are out shopping for stones.
None of these have been irradiated, so I wouldn't expect them to have any detrimental effects on health; however, these are ways that stones are either altered from their natural state, or created entirely by man. It's always good to know exactly what the stones actually are before making the investment in them. I wont' say, "Let the buyer beware", since these things are all perfectly legal and SHOULD be indicated clearly by the seller. But I will say, "Let the buyer be diligent".