Rubies are considered to be one of the four precious colored gemstones that  have been known since antiquity. They typically range from blood-red to pink in color.
The blood red ones are the most valuable and the pink ones are sometimes called pink sapphires. There is no firmly established guideline as to when the name change occurs.

Rubies are among the hardest of gemstones with a MOH rating of 9 (the hardest gemstones, diamonds are a 10--glass is a 5)

Color, cut and carat weight are the prime determiners of price. You will notice in this set that the rubies vary in color.

Since antiquity, most rubies have come from the Mogok Valley in the area formerly called Burma (now Myanmar)

All natural rubies have imperfections including color impurities and rutile needles called "silk".

Almost all of the rubies currently used in jewelry are either man made or the natural ones are heat treated.

If you see a large ruby in a piece of jewelry and it does not show imperfections under magnification, you can be pretty well assured that it is manmade.

ruby gemstone spoons burma thailand
These demi spoons are from either Burma or Thailand. As you can see the colors of the rubies differ, although part of the difference is the lighting source.
The back is only marked 'ss' which I am assuming means sterling silver, but that is definitely an unconventional marking. I haven't acid tested them.
The elephant on the right is nice. These spoons probably date before 1900 and I don't think they have been heat treated (although the process has been available for hundreds of years).

Colored gemstones such as the ruby are heated in computer controlled ovens to just below their melting point. This allows the aluminum oxide in the stone to change its molecular shape and as it cools it creates a new crystal structure.
The chromium in rubies combine with different atoms and creates a better red color. Many different gemstones are routinely heat treated which means that our gemstones are significantly prettier than those of our ancestors.

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