FINISHING OF NATURAL PRECIOUS MINERALS

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Jewelry manufacturing has always experienced a lack of quality raw materials. This causes jewelers to turn to natural high-quality rocks and do the enriching themselves. Enriching is an artificial change of a precious rock’s makeup in order to increase its aesthetic qualities and raise the market price. None of these alterations of the rock’s exterior are related to cutting or polishing.

Truly beautiful rocks are rare in nature. More common are minerals of the “wrong” hues (extremely light, murky dark, insufficiently translucent, et cetera), with features that tarnish the overall view. This is why precious rocks are enriched in various methods. The enrichment’s effect can last for a long time, but the rock’s properties don’t have to change long-term during its use (through wear, cleaning, polishing).

The processing and enrichment of precious rocks has existed for many centuries. This has allowed for many ways to transform said rocks to develop.

Professional gemlogists use the following methods:

  • Radiation treatment,
  • Oil treatment,
  • Radiation,
  • Painting, etc.

Let’s look over these methods in more detail.

Thermal processing

The most common enrichment method for a precious rock is thermal processing. This process gives us the ability to change color, make it brighter or dimmer. Tourmalines and amethysts in particular are often thermally processed for slight enlightening. With today’s modern cleaning methods, we can no longer distinguish whether a gem has undergone thermal processing.

There is thus no difference between the price of processed and unprocessed rocks. Most times the heat enhances the gem’s natural qualities, making it brighter and richer, increasing its market demand. You simply won’t find aquamarine, tanzanite, citrine, pink topaz, blue and colorless zircon, that haven’t undergone thermal processing.Their cost is always much higher than initial material. This is done over decades, and is normally considered part of the manufacturing process. As a rule of thumb (to our dismay!), the heating and color change the semi-precious rock has undergone is not factored at all.

On the other hand are gems like rubies, sapphires and diamonds. The artificial changing of their properties drastically sways the cost. Plus, the turnover of gems is controlled by the government, defended under specialized laws, and maintains much higher requirements. Hence, gemstone enrichment is handled carefully, in specialized situations. For example, in the removal of included rutile (“silk”) from rubies and sapphires and undesired hues (such as the transformation of grey into silver grey). As a result of the heat the color of natural rubies grows richer, removing the undesired (violet) shades. The cheapest enriched rubies are thermally processed, their cracks filled with lead glass. Such a procedure conceals the cracks in rubies, improves the gem’s translucence and brightens the color.

Unprocessed rubies and sapphires contain microscopic needles of routine or tiny bubbles of liquid, which indicate that the rocks weren’t heated. The amount of rubies that haven’t undergone any processing is measured not even in the tens of thousands, but merely in the thousands. The cost of unprocessed gems is comparable to the cost of extremely high-end diamonds. Such rubies are much sparser than diamonds!

Information on other processing methods and the improvement of natural jewels can be found in the second part of this article.

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