What is natural ruby?

This post, based on something I wrote for Helium back in 2011, was first blogged here in 2013. However, it’s a natural tie-in to yesterday’s post about chromium.

The loose gemstone that Alfred the butler described to Master Bruce in The Dark Knight as “a ruby the size of a tangerine” would have been much less interesting had he been talking about “a lump of aluminum oxide with some chromium in it.”

English: Ruby and Kyanite Locality: Winza, Mpw...

Ruby and Kyanite Locality: Winza, Mpwapwa, Mpwapwa District, Dodoma region, Tanzania Exquisite, lustrous and gemmy ruby crystals in matrix, measuring up to 2 cm, together with small, blue crystals of kyanite. (Photo credit: Wikipedia)

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Guest Video: Natural vs. Imitation New Mexican Turquoise

Turquoise made headlines recently when researchers discovered that Mesoamericans had more than one source for this gem that they valued highly. Not all of it came from the Southwest!

However, visitors to New Mexico and other parts of the American Southwest today do see a lot of turquoise. If you’re heading there on vacation, here is a video that shows you what to look for in a turquoise shop.

Featured image: Mr.TinDC, CC BY-ND 2.0

Guest Videos: Gneiss and Gold

It’s great to go for a hike with someone who knows what they’re looking at.

Wait. Gold? You’re ending the video right after mentioning gold?

Well, let’s head up to the Yukon and get some gold in the pan!

But how do you know that the shiny yellow stuff you’ve just collected is gold, not pyrite?

Featured image: Acasta gneiss from Canada, by Mike Beauregard, CC BY 2.0. The yellow color is probably lighting; this rock’s value is only in its age: over four billion years old!

Guest Videos: Chocolate and Geodes

OK, so chocolate and sugar aren’t technically minerals…they’ve still powered a lot of geologists on field trips.

In nature, you don’t know what’s in a geode until you cut it open. This can be a lot of fun, along with watching your YouTube views hit the million mark! (Note: They’re getting close to two million views now, and bless them, they haven’t monetized it. Thanks!)

Guest Video: Saharan Desert Glass

Once upon a time, a shallow tropical sea called Tethys separated Africa and Eurasia, covering what is now the Sahara Desert and connecting the Atlantic and Pacific oceans with an equatorial belt of warm water.

Then, one day almost 30 million years ago, something from space burned in through the atmosphere, either striking our planet near the Sahara’s location or exploding in the air above it.

This impact, while nothing like the event that caused a major mass extinction 65 million years ago, was more powerful than an atomic explosion–strong enough to turn exposed areas of quartz-rich sand into glass.


James St. John, CC BY 2.0

Around 19 million years ago, the Arabian tectonic plate began to collide with Eurasia. Slowly, inexorably, land sealed off and isolated what had been the western arm of Tethys, turning it into the Mediterranean Sea.

For this and many other reasons, the world’s climate changed dramatically, and the Sahara became a desert.

Millions of years later, human beings who knew how to survive and prosper in this great desert came along and used this unusual material for tools and, later on, jewelry.

However, seen under a microscope, the Sahara still harbors jewel-like grains of sand.

Featured image: Western Desert sand grains. Wilson44691. Public domain.


Agustí, J., and Antón, M. 2002. Mammoths, Sabertooths, and Hominids: 65 Million Years of Mammalian Evolution in Europe. New York and Chichester: Columbia University Press.

Giuli, G., Paris, E., Pratesi, G., Koeberl, C., & Cipriani, C. (2003). Iron oxidation state in the Fe‐rich layer and silica matrix of Libyan desert glass: A high‐resolution XANES study. Meteoritics & Planetary Science, 38(8), 1181-1186.

Guest Video: Collecting Topaz in Utah

Topaz is the hardest silicon-based mineral, and its clarity and beautiful color make this a beautiful and very popular gemstone.

Topaz got its name from the island of Topazos in the Red Sea, which is also known as Zabargad Island–once the source of all the world’s garnets.

Besides being confused with those yellowish-green garnets, topaz used to be the name for any yellow gemstone, but today it refers to just one mineral (which comes in several colors and also happens to be Utah’s state gem).

And yes, you can go out and collect some!

Featured image: Rob Lavinsky, CC BY-SA 3.0.

Sources: Wikipedia. 2018. Topaz. https://en.wikipedia.org/wiki/Topaz Last accessed March 30, 2018.

Guest Video: Microphotographs of Gemstones

Microphotgraphy using polarized light yields beautiful art.  It also is very helpful in learning more about a gem.



Tomorrow we’ll check out a couple other ways that microscopy reveals information about places we can’t reach: the deep Earth and the past.