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A Traveler's Guide to the Geology of Egypt

 
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Diorite
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PostPosted: Thu Jul 14, 2005 3:57 am    Post subject: A Traveler's Guide to the Geology of Egypt Reply with quote

I bought this book by Bonnie Sampsell and have been working my way through it. It's a pretty good non-technical overview, although I disagree professionally with a couple of things she says. She's a big fan of the High Aswan Dam, for one. And then she's British, so some of the terminology is weird. As it's written, I'm not bothered by bass-alt, but there's the dolerite problem. In the US we don't use the term. Luckily, one of my professors warned us about it.

And I've discovered the source of another problem I've wondered about. I've always had problems with the descriptions of the so-called Collossi (sp?) of Memnon being called quartzite. I've found that what is being called quartzite in Egypt is the metamorphic rock I know as quartzite, but a quartz-cemented sandstone. In some circles it is known as orthoquartzite, but I prefer quartz sandstone. That explains why is appears so weathered. The metamorphic quartzite is known to be very resistent to weathering.

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PostPosted: Thu Jul 14, 2005 1:20 pm    Post subject: Reply with quote

It is interesting to me that there is an issue with terminology. Usually scientists try to find a uniform definition that is agreed upon globally. It does just create confusion if an American scientists uses a different terminology than say a British one.

Then again my ability to spell certain words will never recover from the fact that I have had both Ameerican and British professors Laughing
My friends joke that I have been known to just alternate the spelling throughout a talk.

The Colossi of Memnon are fascinating statues. They are excavating nearby and are finding some statues in much better condition. There are some images of Queen Tiye that are just beautiful.

When you mentioned "a quartz-cemented sandstone" does that mean that it is a combination of sandstone and quartz? The "cemented" part made me wonder if it was man-made stone (poured like cement). I somehow always thought these colossi were carved.

Would the quartz sandstone be easier to work with? I wonder if the ancient sculptors chose a slightly softer stone to make thier jobs a bit easier and ended up thereby creating something that would not be able to stand up to natural wear and tear.
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PostPosted: Sat Jul 16, 2005 1:51 am    Post subject: Reply with quote

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I've found that what is being called quartzite in Egypt is the metamorphic rock I know as quartzite, but a quartz-cemented sandstone.


LOL We sell this book in our gift shop in the Field Museum. Every time I see it I think of you, Diorite. So, you think it's worth it for a layman such as I to purchase? I know almost nothing about geology but it would be useful to learn more as it pertains to Egypt. I just don't want to buy something that will be way over my head.

And as for what you wrote in the above quote, it seems this is fairly common relating to the geology of ancient Egyptian crafts and industries. I think early explorers who lacked the expertise to identify minerals or substances provided inaccurate names, and these names stuck. Egyptian alabaster is a classic example--it's really calcite. Blue-glazed or green-glazed pottery is another--it's actually neither pottery nor a glaze in the ceramic sense.

Oh well, what's a fellow to do?
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PostPosted: Sat Jul 16, 2005 4:42 am    Post subject: Reply with quote

There's a couple of different problems with terminology. There's the one Kmt_Sesh mentions - misidentifications of materials that stuck. There's also the problems inherent in geology because of its history.

Geology developed as a science starting about 1800. Groups in the various localities developed their own terminology and the communication between them during the 19th century (not dynasty!) was variable. Geologist in the US, UK-Europe, South Africa, and Australia were fairly isolated from each other. As time went on and communication improved and attempts to normalize things like rock names have been made. One of the groups doing this is the IUGS -International Union of Geologic Sciences. However, localized differences in nomenclature still exists. And there is the problem, too, of the names being different depending on the level of the geology one practices. And just try to get everybody to agree! Older geologists tend to stick with what they are using and their students pick up the same usage. Sampsell is retired, so I presume she is older than I am by at least 15 years, if not more.

About quartz-cemented sandstone. Sand is a size of particle, just like gravel and boulder. A sandstone is a rock made of sand-sized particles stuck together. Most sand is composed of the mineral quartz, although you can find sand of other compositions.

Just like what Isisinacrisis mentioned about the sand sculptures, you need something to stick the sand together. Anybody who has gone to the beach sees that you can't just pick up a handful of dry sand and squeeze it into a ball like a snowball. Water that moves through sand after it is buried carries dissolved material that under some conditions is deposited between sand grains filling some of the space to form a "cement" to stick the grains together, doing that job. Depending on location and condition what acts as the cement varies. In the case of the so-called quartzite, the cementing material is quartz also. It makes the sandstone harder than most other cements, but not as hard as in the metamorphic quartzite where the quartz grains are welded tightly together with all spaces squeezed out.

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So, you think it's worth it for a layman such as I to purchase? I know almost nothing about geology but it would be useful to learn more as it pertains to Egypt. I just don't want to buy something that will be way over my head.


I think it would definitely be a good read for you. It isn't very technical and she goes through a lot of the stuff you would need in the first chapter. Besides, I happen to know someone who could answer any questions you have. Laughing

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PostPosted: Sat Jul 16, 2005 5:06 am    Post subject: Reply with quote

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Groups in the various localities developed their own terminology and the communication between them during the 19th century (not dynasty!) was variable.


You mean Ramesses II wouldn't just call on his court geologist to identify this or that stone?

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As time went on and communication improved and attempts to normalize things like rock names have been made. One of the groups doing this is the IUGS -International Union of Geologic Sciences.


This is very much like what happened following World War II. Throughout the war the allies encountered difficulties trying to make their industrial facilities work together to produce machinery and weapons and equipment that all could reliably use; weights and measures were approached differently depending on the country. So it was after the war (I believe) that many countries of the West got together to establish the ISO (International Organization for Standardization). I think that's how it went, anyway.

Perhaps someone should have reminded NASA of that several years ago with that Mars lander or whatever it was that failed because the engineers were using both the metric system and U.S. measurements.

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Besides, I happen to know someone who could answer any questions you have.


Oh, goody, you're at my beck and call, then? I can't tell you how often someone like you might come in handy when I'm working at the museum. Someone's often asking some geology-related question that I don't know how to answer. Shocked
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PostPosted: Sat Jul 16, 2005 5:33 pm    Post subject: Reply with quote

I'm always happy to answer geology questions if I can. Ask away.

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PostPosted: Sat Jul 16, 2005 10:29 pm    Post subject: Reply with quote

Here's one I've often wondered about. Through much of the dynastic period the favored stone for monumental building was limestone. No surprise there; it was plentiful in ancient Egypt up and down the Nile. But the switch was made to sandstone by the New Kingdom. It may have been a change in style that reflected this, or it may be that most of the good-quality, readily available limestone was played out. I never thought of sandstone as a good-quality stone for the kinds of massive projects to which the Egyptians put it to use. Is sandstone strong stuff, and is there a variety of this type of stone in Egypt from which builders could choose?
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PostPosted: Mon Jul 18, 2005 11:22 pm    Post subject: Reply with quote

The properties of limestone and sandstone are quite different, but vary depending on the type of limestone (chalk is very soft, other very fine grained but dense limestones are much better for building) or sandstone (its usefulness depends on how well cemented it is).

Sampsell actually talks about the change-over to sandstone. Her comments are that the stone used was based on location (and even locations were picked for the availability of rock). She says that the major difference is the move of most building to the Luxor region where there are no nearby limestone quarries and the nearest quarriable limestone would require moving the stone over land. There is a sandstone quarry not far to the south right by the river affording easy transportation.

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PostPosted: Tue Jul 19, 2005 12:23 am    Post subject: Reply with quote

So the sandstone usage in the New Kingdom was predominant in the Theban region. I wonder if limestone was till favored in lots of other places? But it's quite impressive nonetheless that they used sandstone at Thebes, given how huge some of the structurs in the Karnak temple complex are. It must be high-quality sandstone.
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