DIY Pyramid Blocks & Tiawanaku Stone – Geopolymer

First off, an apology for not finishing the geopolymer experiments past the first round. I ended up moving from Florida back to California, things got packed, and then other priorities stepped in front.

Starting to look at it again, I did my usual “what has been done” look about. Also, being a bit more video oriented now, bothered to look at YouTube. Turns out the Geopolymer Institute has a youtube channel AND has shown just how to DIY and make your own limestone or harder artificial stones from natural materials.

I ran into these in reverse order. The newer video (March 2019) on Tiawanaku and hard “volcanic” stones first, the limestone second. As the pyramid limestone is the older video (12 years ago!), I’m going to present it first.

In it, they use old disaggregated (rotted) limestone rubble as their major material at 95% of solids. The binder is made from a mixture of kaolin clay, natron (sodium carbonate aka washing soda) and lime in water. The natural limestone in Egypt contains the kaolin already, but their source in the video didn’t have it, so it was added. Natron is found in the Egyptian desert, and lime is made by burning limestone. All inside the Egyptian technical wheelhouse.

The water (12-17% of solid volume), natron, clay and lime are mixed in a large tub, then the limestone aggregate is added. As a damp squishable material like wet beach sand, it is dumped in layers into a wooden mold and tamped. In 4 hours it sets up and in a few days it is fully hardened. It looks like real limestone.

A very quick under 5 minute demonstration:

Definitely a DIY backyard amenable process. Most folks don’t realize that native stone, exposed to weather, has a long slow “rotting” process that turns it into a kind of stone rubble. Eventually the end point of sand and clay is reached. At the base of many exposed rocky areas you can find piles of the stuff. Not everywhere, but common near exposed rocks of some age in places where it doesn’t end up covered in plants. In another source, Davidovits points out that the weak limestone of below the Sphinx in the quarry will disaggregate on standing in water for 24 hours. He proposes that is what they did (as it is too soft for building and much softer than the pyramid blocks). Turn the soft marl into aggregate then back into harder stone blocks.

From that wiki:

Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and silt. The dominant carbonate mineral in most marls is calcite, but other carbonate minerals such as aragonite, dolomite, and siderite may be present. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, formed under freshwater conditions;

The Egyptians did know their mud ;-) Having two of the ingredients already mixed and the third in piles in the desert, all that is missing is lime. Use a chunk of limestone for a fire pit liner and you will form that. Now all that is needed is to pitch some of this stuff on a trash heap / ash pile and have it get wet. And observe…

So, pyramids done, how about those Space Aliens in South America? Seriously, though, why is it any unexplained constructed thing, the “Go To” answer is Space Aliens or a Pan-Global High Tech Lost Culture. Can’t it just be they knew a little chemical trick we’ve forgotten?

In this one, the technology used to unravel the source of material is much more advanced. Scanning Electron Microscopes (SEM) and X-ray spectrometer (EDS) analysis of minor specs in the rocks. Using this, they trace the origin of the rubble used to a particular site. There is a red “sandstone” and a harder “volcanic” andesite. For the harder “volcanic” stones, they have not yet had permission to test the likely source volcano just over the border in Peru, but do find that the use of phosphate causes the proposed mixture to precipitate to stone. But where to get phosphate? How about a guano island?

Then they show the historic shipment routes of the guano, and upon mass spec. analysis of the inclusions in the “volcanic” stone, find organic bits and the same elemental signature as the source guano. Pretty much nails it down.

The sandstone is made fairly simply with an alkaline binder and the andesite in a more complicated way with an acidic binder.

Sandstone:

Rotted stone (sand / clay mix), Natron (Sodium Carbonate / washing soda), water.

His accent is a bit thick and my ears not so good, but I think he called it weathered sandstone and clay. (Also note he pronounces llama properly as YaMa…) As sandstone is a mix of quartz, feldspar and clay bits, and those are in just about all rocks in various degrees, this technique ought to generalize to several kinds of source materials. Even rotted granite has similar basic materials in it, you just need to make up whatever is missing to the “right” degree.

Note that when he talks about albite, it is a Sodium Aluminum silicate, likely formed from the sodium polysilate in the mixture when first made. https://en.wikipedia.org/wiki/Albite

Andesite:

Unknown volcanic rubble, water, organic carboxylic acid (vinegar or oxalic or similar carboxylic acids) then neutralized with phosphate / guano. As you can buy both vinegar and oxalic acid by the gallon these days and phosphate is as close as the garden store, this, too, becomes a simple DIY at home technique. Many folks have explored the native legend of using plants to soften stones, and succeeded at making the stone into mush, but then could not harden it again. They key bit there is the phosphate.

My speculation on the “tube drill” holes in Egypt (where they have spiral cuts in hard stone that would require diamond drills and tons force with current tools) is that they simply used an organic carboxylic acid to make the stone softer and as a lube while they did the cutting. Davidovits (who knows far more about this than I do) says this only works to dissolve limestone, so it may require a different material as the softening agent, or maybe it still softens ‘just enough’ for a hard tipped drill).

A VERY detailed scientific analysis of the entire local geology, potential source sites, microscopic, spectrographic and SEM analysis of it all and more.
1 hour+ a minute:

As I’d often said I thought the stones looked like they were cast, not carved, I’m happy.

Think if maybe we used stone bowls and pestles and cups and all for processing and cooking our plants, we might have noticed a long time ago that they softened under carboxylic acid mixes? Note that Citric Acid is one of this class. We can now buy it in small bottles in the canning department of stores (where folks still do canning…). So what happens when some “primitive” housewife complains to her stone working husband that his pestle isn’t so good as it wears very quickly when making orange juice? Hmmmm? Or maybe she just figured out to use the softened end bits to make some pretty beads with easy to form holes in them and then hubby asked “Hey, how’d you do that!?”…

Never underestimate the power of simple observation over long periods of time. I don’t care much how smart or educated someone is; it is far more valuable that they are a keen and objective OBSERVER. Nature gives us a thousand “experiments” a day, all we need to do is observe well and consider.

So now, armed with a much better theoretical foundation, I can set about trying to make my own small bit of geopolymer and maybe catch up to where the state of the art was 30 years ago (or 3000 years ago…) For “only” $130 you can get his book on how the chemistry works…

https://www.amazon.com/Geopolymer-Chemistry-Applications-4th-Ed/dp/2951482094

So I think I’ll be using the old trial and error and internet approach instead…

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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48 Responses to DIY Pyramid Blocks & Tiawanaku Stone – Geopolymer

  1. Keith Macdonald says:

    Glad to see you back on the geopolymer topic. :-)

    A while ago I had the chance to talk to a geologist attached to English Heritage, looking after Avebury Stone Circle. I asked what kind of stones were used. The first answer was “Oh, they’re sarsen stones”. Yes, but what are the sarsen stones made of? “Oh, these are concreted alluvial deposits”.

    I asked “Oh, you mean they’re made of concrete, like some of the pyramids?”. At this point the English Heritage geologist was starting to look a bit scared, so I stopped asking awkward questions.

    And yet : some other geologists like Steve Marshall are more enquiring. They’ve noted many curious things about the sarsens at Avebury, and have even made their own geopolymer sarsen stones. :-)

    See http://exploringavebury.com/geology
    and http://exploringavebury.com/assets/uploads/files/Making%20Sarsen%20Stone.pdf

    As for the Egyptians drilling through “solid stone”, would it be too bleeding obvious to suggest that they were drilling through geopolymer concrete *before* it had set hard?

  2. Larry Ledwick says:

    Another option on the drilling hard stone, is while researching how the Easter Islanders carved their stone idols they found that if they splashed water on the stone then struck the wet stone with a hammer stone it removed a lot more stone than if they did the same operation dry.

    There could be other options for example using a hard sharp sand and a wooden mandrel spun in the hole with a bit of water, You would get lots of wear on the wooden mandrel but you would also cut the stone with sand that is nearly as hard as diamond.. Now if the lubricating fluid was acidic water ???

    Time and persistence sometimes out performs brute force and high technology.

  3. Larry Ledwick says:

    Found it – using sand as the tool to cut granite.
    https://www.pbs.org/wgbh/nova/lostempires/obelisk/cutting.html

  4. E.M.Smith says:

    @Keith Macdonald:

    OMG, I’d not thought of that… so bleeding obvious once you’ve said it! They were casting the block and while it was still semi-soft, ran a drill into it. My God I think You’ve Got It!

    @Larry L:

    As a general technique, yes that would work. What says the Egyptians were doing something different is the spiral grooves that cut something like 1/10 in. at a turn and is clearly made by ONE cutting point, not the horizontal banding you get with slush cutting. Here’s what I think is an Australian pointing out the issues in some detail.

    Now, given Keith’s insight, and knowing they were already making cast stone, it is clearly an assumption everyone is making (even me…) that they were cutting hard set stone. But after a few hour set, there is a several days hardening period. It would make perfect sense to do a rough casting, take the mold off, then polish, drill and fit out while it was workable like a chalk…

  5. Tim. says:

    You get a good view of Tiwanaku from Google street view.

  6. Graeme No.3 says:

    Larry Ledwick:
    Thor Heyerdahl did some experiments with carving on Easter Island. They found that the stone in the quarry was very hard on the weathered surface but once through that was much more easily ‘carved’ with rock hammers.
    Tube drilling is known in lapidary work e.g. chinese. Use a hard abrasive and a bow drill. These days carborundum or industrial boort (synthetic diamond) but whatever was available. They cut through jade, one of the toughest (not hardest) stones. Where the ancients using crushed quartzite or agate etc.? Much more likely that they were cutting manufactures stones while they were soft.
    Cutting Granite or Basalt would definitely need hard abrasive and lots of hard work.

    EMS. Definitely an australian but the conclusions aren’t necessarily mine.

  7. Another Ian says:

    O/T? Well it mentions archaeology and a clay pit!

    “The remains of an ancient ape found in a Bavarian clay pit suggest that humans’ ancestors began standing upright millions of years earlier than previously thought, scientists said Wednesday.”

    http://www.smalldeadanimals.com/index.php/2019/11/07/the-sound-of-settled-science-61/

  8. E.M.Smith says:

    @Another Ian:

    Every so often you get folks talking about “Ancient HUMAN footprints!!” and they forget that the human like foot evolved long before the rest. IIRC, Lucy had one more or less. We’re talking a million or two years back. So most likely the folks saying humans have been around for a million years mean human ape like ancestor that walked like we do…

    In Africa they found a transitional form from near the Lucy dig but about 4 million YA IIRC that has a halfway opposeable big toe, and can both climb trees and walk upright. I suspect the reality is that there were several species of great ape and some walked, some climbed, some knuckle walked, and some were runners of the plain (what we became). What survives isn’t what was there, and what fossils are found is a trivial subset orthogonal to now. Oh Well.

    OTOH, 12 MYA is a lot further back than 4 MYA, so it is still a big deal. Personally, I’d rather have the semi-opposeable big toe and be a lousy runner but climb well (and maybe hold the coffee mug while I type ;-) since I already don’t run well… I have a “high illiac crest” with a pelvis a bit more like chimps than Cro Magnon… sort of Neanderthal like…

  9. Larry Ledwick says:

    Reading this wiki on natron makes it clear that the Egyptians would have been very familiar with the chemical behavior of natron as it was used in some of their other arts and processes.

    https://en.wikipedia.org/wiki/Natron

  10. H.R. says:

    Wait ’til they find out that the 12 myo Adidas-wearing-prototype-human noticed that when he chewed certain leaves and spit on certain stones, they softened up enough to form a nifty axe head without all that tedious chipping and grinding using other stones.
    ;o)

  11. E.M.Smith says:

    @Jim2:

    Been there, done that. ;-) Very early on I learned to bake baking soda to make washing soda… About the time I had my first chemistry set. 8 years old? Also made ammonia and ammonia water (and eventually some very mediocre detergent. I’d made soap and thought I’d try something harder…). I was sort of into cleaners for a while… don’t really know why… maybe because I used a lot in the restaurant… I was the “dishes, pots, and floors” kid… (the older sisters waited tables…)

  12. jim2 says:

    EM – I can relate. I made soap in the sixth grade I think it was, and like you, had a few chemistry sets at an early age, then put together some of my own. That I’m alive after all that is nothing short of a miracle :)

  13. YMMV says:

    The DIY pyramids video didn’t say it, but it shows them building the blocks in place, not casting them at the bottom and hauling them to the top of the pyramid with ramps, ropes, and slaves.

    When did chemistry sets go out of fashion? They still exist, but plastic instead of glassware. Not cool. Wouldn’t you know it, Wikipedia has the answer. 1969.
    https://en.wikipedia.org/wiki/Chemistry_set
    https://www.smithsonianmag.com/science-nature/the-rise-and-fall-and-rise-of-the-chemistry-set-70359831/
    https://www.sciencehistory.org/distillations/chemistry-at-play

  14. Larry Ledwick says:
  15. Yes Jim2, can say the same about being alive. i remember making ammonium triiodide. Thought it fun to put it on the door knob for the teacher. Had an explosion in my room once when a sample was a bit moist and I left a vial on top of the heater.The glass completely disappeared and the house shook followed by words from parents.

  16. Christian says:

    Related video on building with big stones. I can’t remember where I got it, maybe from you? https://www.youtube.com/watch?v=E5pZ7uR6v8c

  17. andysaurus says:

    Surely [I know, don’t call me Shirley] this explains how the pyramids were constructed, without all the ramps. Just take baskets of the concrete mix up and make the blocks in situ. It also explains how they could be so closely aligned. Please let me know if I’ve missed something obvious.

    On another tangent from my mind, when they were tamping the concrete down in the molds, were they chanting RAMses RAMses? Just a thought.

  18. E.M.Smith says:

    @AndySaurus:

    That was the goal in doing it this way; to demonstrate what Davidovits thought most closely approximated the stones of the Pyramids including their exactly matching joints and their variations in surface textures (water in mix vs weather at time of setting).

    As per what they were chanting, Ramsis works for me, though I’m also fond of Hqt or tnmw or even haAmt ;-)

    Beer was generally known as “Hqt” (“heqet” or “heket”), but was also called “tnmw” (“tenemu”) and there was also a type of beer known as haAmt (“kha-ahmet”). The determinative of the word Hqt (beer) was a beer jug.

    From: https://ancientegyptonline.co.uk/beer/

  19. cdquarles says:

    I’ve long considered that the Romans poisoned themselves with lead, mostly acetate or citrate (aka sugar of lead), and not so much the fairly low acidity of natural rain (carbonate, nitrate and sulfate), though that likely contributed. Didn’t they know enough to keep the water pipes separate from the sewage ones? ;) or is it my memory fading?

    As you say, being observant and found that orange juice on a lead plate tasted sweet.

    I also had a chemistry set (purchased at the variety/drug store on the main drag) from ca age 9. I made all sorts of lovely stuff to play with (and yes silicone polymer was one of the things you could make).

  20. agimarc says:

    Andesites are a very common volcanic rock midway between basalts and rhyolites. in the volcano world, it has sat below the surface for a while and chemically “evolved” a bit. Mostly found from subduction volcanoes, so you will see a lot of it around the Pacific rim, think Alaska, Kamchatka, Kurils and Japan. Also see a lot of it in Indonesia and the PI.

    More interesting to me are the welded tuffs – what I used to call sandstones in the SW US. These are sheets of pyroclastic flow meters to hundreds of meters thick easily cut by running water. Crumble this stuff up and it can be used for geopolymers, like the Romans used volcanic ash to make their concretes. Cheers –

  21. E.M.Smith says:

    @CDQuarles:

    The Romans also used lead cookware. One fish sauce was particularly prized. It was boiled down in a large lead pot and made a lead salt… I’m not sure if it is the same, but there was a wine sauce similarly made that was sweet. (Guess why…)

    It wasn’t just the water pipes, it was the nature of their preferred cooking and sauces… Also the women would make their faces pure white with a white lead powder… Lead oxide?

    They did have separate water supply and sewage. The aqueducts mostly went to pubic fountains where folks could fill up their jugs (very rich connected folks might get a line to the home….) and then the public toilets and street drains ran into sewers to the “cloaca” dumping out away from town. Fairly smart system, really. Run a small river through town, split out the drinking / cooking / whatever water and then have the sewage and everything else washed out downstream with the excess.

    But don’t have their dishes with reduced wine sauce…

  22. cdquarles says:

    @ agimarc,
    That’s interesting … yet chemistry is still chemistry and Egypt is in a rift valley … (and I also what silica would look like precipitating out of critical point water, instead of critical point carbon dioxide). Has any geochemist considered the effects of critical point water on Earth’s minerals? If so, could someone point me to said geochemist(s)? [I have seen quartz with inclusions that, to me, could have been the result of critical point water going subcritical.]

  23. E.M.Smith says:

    @Agimarc:

    It’s another one of those “in retrospect” things… There’s a LOT of marl and tuff and other friable stone all over the place. So which is easier: Taking on that #$&@ hard sold stone and cut / dress a chunk of it using primitive tools, or, find some goober to make the loose stuff stick together?

    I’ve driven past huge piles of tuff, clinker, volcanic cones, rotted sandstone, some rotted granite and more. Even climbed on some granite that had the surface crumble if you worked it a bit too hard. IF you lived in that constantly, it would be seen as an easily gathered and used material resource. Then all you need is the “lucky accident” that has some of it used next to a lake deposit of Natron… all over the place and in the dry lake beds of California, too, in places.

  24. jim2 says:

    Supercritical water in geologic processes:

    https://file.scirp.org/pdf/AJAC_2014012712561901.pdf

  25. Another Ian says:

    Did the output from the beer help with the rock making?

  26. E.M.Smith says:

    I think it was the input of the beer that helped :-)

  27. cdquarles says:

    Oh, thanks, Jim2. From 2013! I wonder …. and I am reading it now. That’s an interesting paper. Only some of the potential chemistry got discussed. Oh well. The search goes on.

  28. beththeserf says:

    The geopolymer theory solves many problems… no wheels, no pulleys, no steel tools – Occam’s Razor.

  29. H.R. says:

    @beth – Are you getting any ideas for maybe a 1/4-scale Stonehenge in the backyard as an interesting garden feature? ;o)

    Myself, I’m thinking of a 30′ base pyramid to set off the koi pond. It won’t be strictly authentic, but I could have a waterfall come out of the top and flow into the pond. Not everyone has one of those, doncha-no :o)

  30. beththeserf says:

    H.R. i/4-scale be danged. Full scale sun dial, nothing less. I gotta few acres. )

  31. H.R. says:

    Beth – Get the neighbors to help, beer provided of course, and it’s a weekend project. :o)

    That’s probably how it went down with the original. Stonehenge… the results of a drunken party where some said, Hey, y’all! I got an idea…”

  32. Larry Ledwick says:

    Well of course someone had to say “here hold my beer” before they put the cap stone on the top of the uprights!

  33. beththeserf says:

    Yes, HR. As I come from the land down under, guess I’ll hafta’ invest in a Kombe of Victorian Bitter. Hmmmph,back when I was a young serf, BC, (before coal,) it was all slave labour.

  34. andysaurus says:

    @beththeserf and Graeme #3 and me + others, all Aussies (Although mine is by choice, not birth). Funny how we all gravitate towards the most sensible blog post on the net. Anybody who has read Neville Shute’s Beyond the Black Stump will recognise the argument that Aussies and Americans have a frontier spirit in common. Perhaps it’s true, even though I sat behind a keyboard for all my working life.

  35. H.R. says:

    This video popped up as a suggested ‘further interest’ after one of the music videos finished.

    It isn’t as good on the hard scientific evidence presented in the second video (like!) and it has a bit of mysticism sprinkled through it. It’s not very rigorous. But it had several things going on which had me sitting through it.

    1) A granite cave site I hadn’t heard of before

    2) Interpretation similar to what we’ve been discussing here; older, more technologically advanced civilization that was lost due to the Younger Dryas (discussion of that towards the end). Surviving population not able to get back to the old level of tech.

    3) Lots of good images of various megalithic sites – not just the cave – the show a mix of using the stone softening techniques and the geopolymer moulding technique. As they show the different sites, you see the contrast where they softened and fitted boulders or softened to cut quarried stone vs obviously moulded-in-place construction. Bonus – good images of small stone and mortar construction on top of the higher tech megalithic construction showing that earlier tech was lost.

    4) They mentioned or hinted at aliens, but didn’t seem to buy into that. They briefly mentioned that as a belief by others.

    So… if you don’t have time at all to watch or maybe just time to FF through to check out the different sites, then the take home is that others are reaching some of the same conclusions we have been discussing above, minus the more detailed tech aspects we discussed.

    Here ’tis.

  36. H.R. says:

    Oh! Speaking of different sites and techniques, what about Petra, Jordan?

    It seems obvious to me that it was made by people re-learning stone working technology. They may have been aware of stone softening, but not how to harden it again, so no moulding.
    .
    .
    .
    I note regarding stone softening technology that it was lost for centuries, maybe millennia, and only recently have we re-discovered it, what, around 1940 it was? Once you discover that, then it’s a matter of figuring out how to harden it again. We’ve figured it out relatively quickly. It looks like there was a time where softening was known, but not the hardening part.

    Then we got metal tools and variolous material moving mechanisms and went with that tech for working stone.

    Now, if we want to go back to moulding stone megaliths, just think of what we could do with a few modifications to some of the giant Caterpillar equipment; dig tons of the materials in a single scoop, transport cubic yards and yards in a single load on the earth movers, pound huge moulds solidly with hydraulic rams. Easy peasy to combine modern and ancient tech, eh?
    .
    .
    .
    P.S. – In grade school in the ’60s, I was taught that mold was something you didn’t want on your bread and a mould was something you used to cast useful parts. It wasn’t a British vs American English thing. My spell check is telling me that American English has dropped the distinction because I keep getting ‘mould’ highlighted as being wrong. I would have gotten points off if I had written the above for homework back in the ’60s.

  37. Graeme No.3 says:

    @cdquarls & E.M.S.
    Lead acetate used to be known as Sugar of Lead, as it tasted sweet.
    Oxidised alcohol makes vinegar (dilute acetic acid). The Romans were fond of vinegar (and lead vessels).
    Sugar of lead was one of the first preservatives used in the British wine trade. When they switched to portuguese wine (from French from Bordeaux although then made inland) they found it “a bit rough”. Most of the wine was shipped in wooden casks and the extra time and vibration meant more oxygen and bacteria etc. into the wine, hence shorter life. Adding ‘sugar of lead’ acted as an antibiotic AND sweetened the wine, improving sales.
    A few years later the merchants noticed that their best customers were all dying and petitioned the British Government to ban the use of ‘sugar of lead’. One of the first food laws passed.
    About this time they also discovered adding brandy also acted as a preservative, without reducing sales. Then glass bottles also came into use.

  38. Graeme No.3 says:

    E.M.S.
    The surface of the pyramids was smooth and shiny; impressive in the sun.
    This would involve some intricate moulding. Perhaps it was done in situ?
    Once set enough and fairly smooth (extra water?) it could be polished. (I assume they started at the top and worked downwards).
    This facing was removed by later rulers for other work (cheaper than polishing rough stone) hence only the very top bits are left.

  39. E.M.Smith says:

    @Graeme No.3: I would expect the same techniques used to get glossy cement (wet trowling) would also work on geopolymer.

  40. p.g.sharrow says:

    While doing tests of soil cements here, I mixed our subsoil, a kind of old Lahar of rotten volcanic ash and clays with Masonary Lime with water until it began to develop the bentonite clays. Then poured it out and let it set for a few hours. It became dense as modeling clay and could be shaped , After it set for a day you could carve and polish it. After a few weeks cure it was a weather proof sandstone. Keeping it damp for a month helped with the quality of the cured stone. Adding clay and lime to a baged cement mix made a very strong mortar mix that really glued the stones of my cabin walls together, much tougher then any standard mortar mix. you can not break the bond even with a hammer…pg

  41. E.M.Smith says:

    So you reinvented the geoploymer eh? Nice one.

  42. jim2 says:

    Hmmmm … if Egyptians could cast synthetic stone, then they could have had the equivalent of a printing press!!

  43. E.M.Smith says:

    @Jim2: There is a thesis that the really sharp hyroglyphs were made with carved “type” put in the mold when the objects were cast… so printed, in a way.

  44. jim2 says:

    Of course they had clay. All they would have to do is make a clay negative, fire it, then make copies.

  45. Graeme No.3 says:

    2 items from the author; firstly the presence of fibres in the egyptian sones. Secondly the presence of whole shells on the surface of the blocks. (I am assuming that his synthetic surfaces match the ancient block surfaces, which is implied in the claim by others that the blocks must be natural). If the blocks were chopped out of a solid layer, where are the tool marks, esp. signs of shell damage on the surface?

    3 p.m. Adelaide 41℃ (106℉) today (and probably a bit more to go). I wonder how fire resistant these products are?

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