View Full Version : heating stones

19-05-2005, 02:19

Was wondering if any one knew which stones can handle 225 Farenheit for 1/2 hour.

THE REASON...I've started working with polymer clay, and you have to bake it. I would love to make peices with amathyst, jade, rhodenite and other stones baked right in..but I don't want to rune the stones...

Any suggestions would be helpful


19-05-2005, 02:50

I don't know if you can heat the stones, but I was thinking maybe you can make the indentations before baking and afterwards just glue the stones onto the baked clay. This way you don't have to heat the stones.

Just a thought,

19-05-2005, 03:03
MM ~ I read that if you heated fluorite, it would glow, so I tried putting a piece in a smoking hot frying pan. It didn't perceptably glow but it didn't crack, either. So you'd be fine baking that at 225. BB, Stella

19-05-2005, 03:32
You need to find out which stones will change colors when heated. Amathyist will turn yellow this is how they make citrine. If a clear cyrstal has any additives like iron or such that you can not see they will color it under heat. It all depends on what is in the stone.


19-05-2005, 05:21
I would think though that at 225 F there should be no problem at all! Even at 225 C I would not fret. Usually stones would change properties at a few 1000 degrees, I'd think.

What you could do is try with one if you want to be absolutely sure?


19-05-2005, 05:35
If you go here: http://www.gemcutters.org/LDA/Archive/html%20files/LD182.htm you'll find the International Lapidary Association's Digest. If you scroll down, there is a short message about baking smokey quartz in bread to turn it yellow (and I've heard clear, I guess depending on how dark the crystal was to start). The author laughs at this, but not at the claim that the heat changes the stone's color, but at the concept of baking it in bread. He does make a valid point. Anyway, it would seem that baking some crystals in low temperatures can change their color (sometimes this is a desired effect of heating) and can shatter them which would never be a desired effect. ;) He has his web site and email listed. I haven't check to see if he has any info on his site that could help you, but you might want to take a look or even try writing to him and asking if he can point you to a resource that would give some sort of temperature tolerances for various crystals and minerals.

Good luck!

19-05-2005, 06:07
Heat and Stones are a tricky combination.
Each stone has it's own tolerance of heat and they all vary.
Someplace there is info about the temps. stones can take and the amount of time that they can be heated before they start to change or crack, but I don't know where to begin to look.
The only suggestion would be to experiment with lowering the temprature and extend the time of baking the clay & stones.

19-05-2005, 10:33
Stones have been heat treated for years to improve colour and clarity especially ruby and sapphire. Amethyst is treated to remove smokeyness and lighten colour in stones to dark. That would be the result of low heat although I am not sure what degrees that would be at I think about 300-400 degrees higher heat would turn it to citrine but it would be possible for it to happen at a smaller heat as everystone is different. Jade and Rhodonite are not usually heated I am not sure of the effects. Here's a list of gemstones that are not commonly treated if stones you are thinnk of using appear on this list I probably would reconsider baking them:

Adamite **
Alexandrite (faceted and cat's eye)
**Anhydrite (Crystal)
**Apatite (Cats Eye)
**Apatite (Rough)
**Apophyllite & Stilbite
**Apophyllite (Crystal)
**Aquamarine (Crystal)
**Aventurine (Blue)
**Aventurine (Green)
**Axinite (Crystal)
**Azurite (Crystal)
**Azurite Malachite
**Barite (Crystal)
**Barite and Pyrite (Crystal)
**Calcite (Crystal)
**Celestite (Crystal)
**Cerussite (Crystal)
**Chalcopyrite & Quartz
**Chrome Diopside
**Chrome Diopside (Cats Eye)
**Chrysoberyl (Cats Eye)
**Chrysocolla (Gem Silica)
**Chrysoprase (Imperial)
**Cinnabar, Calcite and Quartz
**Creedite (Crystal)
**Cuprite (on Chrysocolla)
**Danburite (Mexico)
**Diamond (Natural Champagne)
**Diamond (Natural Cognac)
**Diamond (Natural Fancy Colors)
**Diamond (Natural White)
**Diamond (Natural Yellow)
**Dolomite (Crystal)
**Enstatite (Cats Eye)
**Epidote (Crystal)
**Fluorite (Bi Color)
**Fluorite (Chrome)
**Fluorite (Color Change)
**Fluorite (Neon)
**Fluorite (Tri Color)
**Fluorite and Galena (Crystal)
**Fossilized Dinosaur Bone
**Fossilized Fern
**Fossilized Mammoth Ivory
**Fossilized Orthoceras
**Fossilized Paraceratherium
**Fossilized Stegodon
**Fossilized Trilobite
**Garnet (Color Change Rough)
**Garnet (Color Change)
**Garnet (Demantoid Crystal)
**Garnet (Demantoid)
**Garnet (Green Garnet)
**Garnet (Green Uvarovite)
**Garnet (Grossular Crystal)
**Garnet (Grossular Mali)
**Garnet (Hessonite)
**Garnet (Malaia Rough)
**Garnet (Mandarin)
**Garnet (Mint Green)
**Garnet (Mozambique)
**Garnet (Rhodolite Rough)
**Garnet (Rhodolite)
**Garnet (Spessartite Rough)
**Garnet (Spessartite)
**Garnet (Watermelon)
**Hematite (Crystal in Quartz)
**Hemimorphite & Calcite
**Hemimorphite (Crystal)
**Huebnerite (with Quartz)
**Iolite (Cats Eye)
**Jade (Imperial)
**Kunzite (Cats Eye)
**Labradorite (Facet)
**Labradorite (Rainbow Cab)
**Labradorite (Rainbow Facet)
**Larimar (Pectolite)
**Lazurite (Crystal)
**Marcasite (Crystal)
**Microcline (Crystal)
**Moonstone (Cats Eye)
**Moonstone (Rainbow)
**Muscovite (Crystal)
**Obsidian (Mahogany)
**Obsidian (Snowflake)
**Opal (Cats Eye)
**Opal (Crystal)
**Opal (Jelly)
**Opal (Multi Color)
**Opal (Pink)
**Opal (Semi Black)
**Opal (Yellow)
**Opalized (Sliced Ammonite)
**Pyrargyrite (Crystal)
**Pyrite (Druzy Rainbow)
**Pyromorphite (Crystal)
**Quartz (Crystal on Stellerite)
**Quartz (Crystal)
**Quartz (Imperial Cats Eye)
**Quartz (Pink)
**Quartz (Rose)
**Quartz (White)
**Rhodochrosite (Crystal)
**Rosasite (Crystal)
**Rubellite (Rough)
**Ruby (Unheated Mogok Rh.)
**Ruby (Unheated Mogok)
**Rutile (Cats Eye)
**Sandstone (Natural Green)
**Sapphire (Crystal)
**Selenite (Crystal)
**Siderite (Crystal)
**Sillimanite (Cats Eye)
**Smithsonite (Crystal)
**Spinel (Crystal in Host)
**Spinel (Fancy Colors)
**Spinel (Noble Red Crystal)
**Spinel (Noble Red Rough)
**Spinel (Noble Red)
**Star Diopside
**Star Sapphire (Burma)
**Star Sunstone
**Stibiconite (Crystal)
**Stibnite (Crystal on Calcite)
**Stibnite (Crystal)
**Sunstone (India)
**Sunstone (Oregon)
**Tigers Eye (Blue)
**Tigers Eye (Golden)
**Tigers Eye (Iron)
**Tigers Eye (Red)
**Topaz (Crystal)
**Topaz (White)
**Tourmaline & Quartz (Crystal)
**Tourmaline (Cats Eye)
**Tourmaline (Crystal)
**Tsavorite (Rough)
**Uralite (Crystal)
**Uvite and Magnesite (Crystal)
**Vanadinite (Crystal)
**Vivianite (Crystal)
**Wavellite (Crystal)

01-06-2006, 15:11
MM ~ I read that if you heated fluorite, it would glow, so I tried putting a piece in a smoking hot frying pan. It didn't perceptably glow but it didn't crack, either. So you'd be fine baking that at 225. BB, Stella

I recently put a couple of small fluorite peices on a hot wood stove oven (on not in) and while i didn't check to see if they were glowing, they most definetly retained the heat of that stove for quite some time. not sure if I woudl want to hold a glowing peice of fluorite.

02-06-2006, 21:29
I once made an incense holder in the shape of a striking cobra with red eyes made of Carnelian. After the burning, the Carnelian had not turned to a darker red (as I had supposed) but to a very funny white. So I'd also suggest to bake the clay without the stones in it, but to glue them on later.

14-06-2006, 05:41
Here in Poland there's a man who developed his own method of healing: a massage with heated crystals. I don't know any details, I saw his book in a bookstore and took a quick look into it. If I remember correctly, the stones were heated in water before applying, but I don't know what kind of crystals were used in this method. I guess I'll seek this book again and check it out.

But something from my own experience: I have an aventurine, which is the dearest from all my crystals to me (once it literally healed my broken heart, it was my most amazing experience in this matter). I used to carry it in the pocket of my jacket, and unfortunately I used to hang this jacket above an electric heater forgetting about the stone. The aventurine was always very hot and after some time I've noticed that it had changed, I could barely feel its vibration. I tried to recharge it, but placing it in the sunlight or on the amethist cluster helped only a little.

Two days ago I bought another aventurine and compared it with the old one. Both have the same characteristic vibration, but the old crystal is very weak, whilst the new one is strong and fresh. I'd really like to heal this stone, because it gave me so much. And now I know that one should be very careful with heat, as it can damage crystals or change its properties...