Thursday, July 31, 2014


The US Geological Survey does not employ gemologists – while there have been several within our ranks historically, they have been amateur gemologists who have pursued their interest on their own time. Nevertheless, gems DO come from the ground, and could reasonably be construed to be an ultimate product of geology. The following question is typical of the kind we receive about gems.

Q:           Is there somewhere in California near Modesto that I can have a rock collection looked at? We are almost positive that we may have found some raw rubies! They have passed the scratch test and are very heavy and hexagonal shaped. 209-xxx-xxxx
- James

A:            We can't do gemology for you - the US Geological Survey is tightly constrained to work on only particular national objectives that Congress sets, including mineral resource assessments, volcano hazards, etc. 

My recommendation to you is that you contact a local gemological society and ask for guidance. I would NOT recommend going to any jewelry store, as they only focus and specialize on the end products. 

You might try: ... but keep in mind that this is a trade association of retail jewelers, independent appraisers, suppliers, and selective industry members, and only incidentally will they have any component that might be of help to you. 

           You would probably do better with:

...or even better with a local society of educated amateurs, like the San Diego Mineral and Gem Society:

Finally, please keep in mind that there are beryls and other igneous minerals like garnet and eudialyte that can easily be mistaken for rubies by inexperienced people. A true ruby is a pink to blood-red (so-called “pigeon blood”) colored gemstone, a form of the mineral corundum (aluminum oxide). Ruby has a hardness of 9 on the Mohs scale, and is considered one of the four precious stones, along with sapphire, emerald, and diamonds. The red color in a ruby is caused mainly by the presence of the element chromium in the crystal lattice.

Thursday, July 24, 2014

The Dust Bowl, King Solomon, and Country-Western Music

Sometimes – even after all these years – I am amazed to learn of yet another series of cultural connections all tied together by geology. The following Q&A is just one of many examples of this. Another example is how modern Venezuelan politics and its history are underlain both literally and figuratively by its ancient Archaean geology. This Venezuelan example would take too long to share here, but it can be found in a book my wife and I have written titled “2 Worlds, The Real Venezuela: Living on the Edge of the Jungle and the Rise of Hugo Chavez” ( By the way, the girl holding the monkey in the cover photo is our youngest daughter.

Q: I just watched a show on the history channel. Part of the show covered the "Dirty 30's" and how the "Dust Bowl" helped shape human kind today. My question is, of the possible millions of tons of top soil blown away. Where did it go? Did the eastern sea board states get a foot taller during those years or what? Thank you for taking the time to answer my question.  Sincerely,
- Bart A

A: The Dust Bowl was caused by improper farming practices that destroyed the native prairie vegetation and their root systems - and didn't replace them. The US Soil Conservation Service (Now the Natural Resources Conservation Service, or NRCS) was created to first understand, then mitigate the consequences of plowing fields in prairies. In 1933, its original incarnation the Soil Erosion Service was created within the Department of the Interior, with Hugh Bennett as chief. Bennett was a visionary soil expert who had been publishing scientific papers on the subject since the beginning of the 20th Century. He practically invented soil science.

       To answer your specific question, yes: the soil goes elsewhere, and other places grow “taller”, though you might not be able to easily recognize this. Winds tend to scour certain localized areas, and then distribute the soil and dust outside these areas - but much more widely. Thus it may not seem like parts of the rest of the country developed deeper soils, but they did - though very marginally. The airborne distribution process drops out the heavier particles at shorter distances, while the finest dust can theoretically blow around the world. You might speculate where some of the dust that always seems to find its way into your house originally came from.

Two anecdotes may help you understand this better.
1. Satellites can see dust from the western Sahara blow thousands of kilometers out into the central Atlantic Ocean. Ultimately it collects in the abyssal ocean depths, where coring has actually measured it and its growth rate. It may even have a part in the Atlantic Hurricane development process.

2. While I was working in central Saudi Arabia two decades ago, I was asked to provide geophysical assistance to a geologist trying to evaluate a small ancient mine (SAM) named an-Najadi. This mine was one of at least 852 small artisanal gold mines found in Saudi Arabia today, and apparently formed the major source of gold reported in King Solomon's treasury.

    While visiting the site I saw that the geologist had used a backhoe to dig trenches. His objective was to get down through the soil to the bedrock, to figure out what the bedrock structure was - so he would know which direction to point or orient his evaluation drilling program. At the bottom of one trench I saw two round stones - they turned out to be grindstones used by the ancient miners to crush the quartz grains holding the tiny fragments of gold that the miners were after. I am looking at those two stones in my office as I write this.

    On the sides of the trench I saw three white lines, and asked the geologist about them. They turned out to be slaked-lime floors of ancient dwellings. I could see the oldest one, then one a meter higher stratigraphically above it - that therefore had to be at least a thousand years younger - and then one above that. The trench was 14 feet (4+ meters) deep. The lowest level was occupied by miners in Solomon's time - 3,500 years ago. The 14 feet of soil above the lowest dwelling level arrived since that time and is called "loess", a German word for blown-in soil. Most of this soil had been blown in from the west. It had come from the eastern Sahara, and crossed the Red Sea to get there. I have personally experienced sand storms in that area that kept aircraft from landing - because pilots could not see the ground for up to three days at a time. Operation Desert Storm in 1990-91 was rushed forward in time to beat these seasonal wind storms called the Shamal. These storms happen during the period of monsoon storms that lash the Arabian Sea for several months in the Spring every year.

    This all tells us that over-grazing in the proto-Sahara, starting thousands of years ago, had already stripped most of North Africa of its protective vegetation, leading to the ever-expanding "desertification" process we see that continues today... and which Oklahoma experienced for a short period in the 1930's.

    Soil conservation is an important lesson we learned from the Dust Bowl of the 1930's. Some of the Oklahoma economic refugees migrated to California, and a country western band leader brought his musical tradition from there - and lived across the street from me when I was a child in Bakersfield, California. I still remember Bakersfield being one of two major Country Western music centers in the country after Memphis... and I can still remember the disparaging name of "Okies" being used for these poor migrants decades after they arrived.

    I hope this answers your question, and perhaps puts it in a wider context.