Heated VS Unheated Gems, learn about common heated gems

Heat treatment is an optimization treatment that is very common in gemstones. We can understand what is the purpose of lower heating? And whether the gemstone you bought has been heated?

Many gemstone merchants will tell you that except for rubies and sapphires, which will be heated, other semi-gemstones are not heated. This is a wrong statement. For example, common aquamarine, topaz, and tanzanite will be heated.

What is a heat-treated gem?

Heat treatment is a common process used to fade, deepen, or even change the color of gemstones. In addition, heat treatment can also improve the clarity of certain gemstones.

Of all gemstone treatment methods, heating was the most widely accepted one. Some viewed it as an extension of the gemstone's natural formation because the earth might have applied heat before the gemstone was mined. Normally, the changes produced by heat treatment were permanent.

One of the most common and conventional heated gemstones is corundum, which includes rubies and sapphires. Unless otherwise stated or the merchant has issued an identification certificate from an authoritative laboratory, it should be assumed that the rubies or sapphires purchased are heated.

Other gems, such as topaz, tanzanite, and aquamarine, are also often heat-treated. Later in this article, Bohilan will introduce you to the effects of heating them up.

Does heated gemstones mean they're not real?

Heating is usually an optimization process, and it is generally believed that heating is an extension of natural processes.

As long as the merchant states that it has been heated and the color after heating is permanent (usually permanent).

Heat treatment is widely accepted in the gemstone industry, which does not mean that the quality of the gemstone is low or untrue.

The benefits of heating gems

Heating the gemstone can improve the color of the gemstone to a more ideal color. At the same time, it can improve the clarity of the gemstone.

Sometimes, heating would make the color of the raw stone change so much that the heated stone would be given a new name, such as Tanzanite.

Disadvantages of heating gems

In most cases, low-temperature heating does not have any disadvantages.

But like rubies and sapphires, which require high-temperature heating, it is possible to make the gemstone slightly brittle.

In addition, there are some other minerals inside the gem, which may expand more than the mother stone gem, causing cracks to appear inside, thus reducing the value and durability.

Heat treatment of gemstones can improve color and clarity. In many cases, heat cannot be detected.

If a seller tells you that the Aquamarine sold is not heated, you should not believe it all.

How do I know if a gemstone has been heat-treated?

Although it is not difficult to find signs that the gem is heated, many times we cannot determine whether it is unheated.

Traces of heating usually appear only when the gemstone is heated to high temperatures (such as rubies and sapphires). These signs of heat treatment are usually detectable.

Ruby and sapphire can withstand high temperatures. They are usually heated above 1000 ° C, sometimes even up to 2000 ° C. However, the inclusions (other minerals) in them sometimes melt or explode at such high temperatures, which is evidence that gemstones are heated.

For many semi-precious stones, it is almost impossible to determine whether it has been heated or not. This is because the heat treatment temperature is relatively low and may occur in nature. Therefore, some laboratories have difficulty determining whether it is formed naturally or after subsequent heating.

Does heating reduce the value of the gemstone?

For gems with lower prices, there usually wouldn't be much of a difference in price between heated and unheated gems. For example, the heated red chalcedony, even if it took on a fiery red color, wouldn't be much more expensive than the untreated red chalcedony.

However, for gems of high quality and higher prices, such as rubies and sapphires, the price would be higher for gems that were not heated and were accompanied by laboratory reports indicating that there was no evidence of heating. The rarer the gem, the higher the premium for the unheated version. For example, a large high-quality ruby with little to no content was very rare, and if untreated, its price could be 3-5 times higher than that of a heated ruby.

For some gems, such as Blue Topaz and Dan Spring Stone, heating may increase the value of the gemstone because most buyers prefer the color after treatment.

Some commonly used heated gems

The following gems are usually heated. Unless there is a lab report indicating that there is none, you should assume that heat treatment has been performed.

Ruby

Heated rubies can eliminate purple and produce pure red.

Ruby with extremely small rutile contents (filamentous) can be heated at high temperature and cooled quickly to produce a more transparent gem.

Sapphire

In an anaerobic environment, heating some sapphires at high temperatures can deepen their blue color, while heating in air can make them lighter.

Sapphires with tiny rutile inclusions (silk) can be heated at high temperatures and cooled quickly to produce more transparent gems.

Pale yellow sapphires can be golden when heated.

Blue Crystal (Aquamarine)

Aquamarine is usually heated to remove green and yellow tones and appear pure blue.

Amethyst (Amethyst)

Amethyst can change color by heating, thus showing a charming purple color.

Some amethysts may be heated to yellow, and some dishonest sellers sell them as more expensive topaz.

Some amethysts may even be heated to turn green, called cordierite. Almost all cordierite comes from amethysts that have been heat-treated.

Tea Crystal

Almost all heat-treated topaz has a reddish hue.

Natural topaz can be heated to change its color from light yellow to the desired orange yellow.

Topaz

Heat some yellow topaz to get pink topaz.

Under the combined action of heating and radiation, the colorless topaz may turn blue, divided into "London blue," "Swiss blue" and "sky blue."

Tourmaline (Tourmaline)

Dark green tourmaline can be heated to lighten its color to emerald green, and its market value is higher.

Tanzanite

Almost all tanzanite is heat-treated to obtain vibrant blue and purple hues.

Zircon

Some brown zircons can become ideal blue zircons by heating in an anaerobic environment.

Warming it in air can also make it golden, red or colorless.

Purple spodumene

Occasionally, spodumene would be irradiated and heated to turn a light gemstone pink-purple.

Mogenstone

Morgenite and aquamarine belong to the same mineral family, and can be heated to obtain more popular colors.

Tiger Eye Stone

Yellow Tiger Eye Stones could turn red when heated, and almost all Red Tiger Eye Stones on the market were heat-treated.

Onyx

The red chalcedony changes from brownish yellow to orange red after being heated.

Smoke Crystal

Smoke crystals with very dark colors can be diluted by heating, and some may even turn yellow, and are sold in the form of topaz.