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Value of Raw, Uncut Rubies

Just like normal faceted rubies, their rough, uncut forms vary significantly in price depending on their quality. Specimens like the star ruby on the right are very common, even with the star phenomena on it. Even cut, these examples are typically not worth $1 a carat, though fine rough like in the example below can be tens of thousands of dollars depending on the parcel.

See those weird curving lines on the common star ruby? That is from when the stone was polished, meaning this is a low-quality polish. Though faint, if not impossible to see, there are other curved lines in two other directions, which are other directions the ruby was polished in.

Common Star Ruby

Cut and Uncut Rubies & Pink Sapphires

17th Century Lapidaries

To the left is an example of what the better-quality rubies look like. Some of these are also pink sapphires since they are both varieties of the mineral species corundum and colored by the same element: chromium. The difference is how intense the red is, though the exact shade that turns a pink sapphire into a ruby is an ongoing debate in the gemological community.

Unlike the common specimen above, these stones of the left are actually transparent, showing much better color and no obvious inclusions (meaning the stone is very see-through). Faceted rough rubies of this quality will never show polishing lines due to how well they’re handled.

A good gem cutter can be the difference between a ruby and a pink sapphire. An untrained lapidary, someone who cuts gemstones, can take high-quality ruby rough and produce a pink sapphire with poor cutting. They can also waste a lot more rough gem weight, and the yields of cut gems are often half to a third of the original rough too under the best conditions

Modern setup for lapidaries

The basic premise of cutting gemstones hasn’t changed much from its beginning to today, with a circular grinding wheel rotating around with diamond dust, and the ruby attached to a stick that is held against the wheel. A lot of this process has been mechanized and cuts redesigned for better gems and output overall, but the final carat weight is still around half to one-third of the original carat weight.

Even if you have a skilled cutter at the wheel, how the gemstone looks inside is not always consistent. There are frequent issues with uneven coloring, like the Mong Hsu rubies from Myanmar and sapphires from anywhere are famous for having colors only surface-deep on the crystal, with the rest of the interior being colorless. While this is hardly the case for every crystal, it is still a possibility. The surface-deep color is not to be confused with diffusion, which is a treatment for sapphires.

 Untreated Mong Hsu Ruby, photo by Ted Themelis

Purchasing uncut crystals can be a bit of a gamble for gem cutters too since every ruby is an individual with different inclusions, colors, and eventually different cuts. An asking price of $10,000 a carat for good ruby rough is hardly unheard of though.

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