All in all it's just another 12 sided block in the wall • /r/badhistory
A recent post I made on Reddit

So over at /r/Pics someone submitted a lovely picture of a masonry block in a wall has 12, yes 12, sides. Amazing, I know. But what really is the most amazing thing about it, are the comments in the comment section. I will give people the benefit of the doubt when it comes to understanding how stonemasons did what they did before power tools and heavy machinery. Rocks are a hard substance. They are hard to break, hard to shape, and when they break you can’t fix them easily. So seeing a rather large block of stone shaped to have many different sides can be mind boggling to some. Some users thought it would take days to do to make, others thought weeks. One user even thought it would take lifetimes to do. What bothers me about all of this are the claims that giants made those blocks or that a geopolymer was used to soften the stone in order to shape it and parabolic gold mirrors were used to direct sunlight to “melt” the stone. I mean, really? What’s wrong with thinking that the Inca, or any other Native American people, used stone tools and hard work to make such wondrous buildings? Is it because they’re brown? Is it because they lacked Guns, Germs, and Steel™? Or does it go back to people fundamentally not understanding how stonemasons do what they do? I believe it is the latter and would like to summarize how the Inca, and quite possibly previous cultures in the region, actually worked stone. This is going to be quite long, quite detailed, and probably boring for some. But construction is my thing. My thesis is literally on construction as well as architectural energetics (the quantification of labor) and labor organization. So this blatant disregard for the abilities of people in the past really gets under my skin so much so that this is going to be my first /r/badhistory submission. So sit back and I hope you enjoy it.

Back in the early-to-mid-80s, Jean-Pierre Protzen published two articles, both titled Inca Quarrying and Stonecutting, in 1983 and 1985. In the articles Protzen wanted to answer several questions. How did the Inca construct their buildings without mortar with precision shaped blocks? Why were the blocks irregularly shaped? How did the Inca stonemasons cut and fit the stones and erect these walls? He even made a passing comment about the mystical “herbal juice” that supposedly softened the rocks as well as “cosmic energies” used. He knew there had to be a better answer so he went out to find it.

Protzen started by examining numerous Inca walls in and around Cuzco as well as visiting several quarry sites attributed to Inca activity. The two quarries he spent the most time examining were Kachiqhata which supplied the red and gray granite used in part of the construction of Ollantaytambo, and Rumiqolqa which supplied much of the andesite used in Cuzco. The Kachiqhata quarry is about 4km from Ollantaytambo across the Urubamba River and 700 to 900m above the valley floor. The quarry itself consists of two giant rockfalls below the cliffs of a gigantic outcrop that has penetrated through an environment of metamorphosed sedimentary rock (Protzen 1983: 183-184). The North and South Quarries at Kachiqhata are the ones that provide most the course-grained red granite found at Ollantaytambo. The grayish and much finer-grained granite found at the site was extracted from the West Quarry (Protzen 1983: 185).

Between Ollantaytambo and Kachiqhata is a ramp that goes down from Ollantaytambo to the river and then up the mountain to the rockfall. Along this ramp route are about 80 abandoned blocks of stone that never made it to the site to be used. The ramp incline varies between 8° and 12° with a width between 4 and 8m. In some instances the ramps are replaced with slides used to transport the blocks more quickly. The largest slide has a 40° incline and runs 250m down a slope. At the bottom were four abandoned blocks. There is also a ramp to the east of this slide for those that don’t enjoy fun. Rumiqolqa had a similar network of slides, ramps, and roads around the quarry to move blocks, but Protzen doesn’t discuss that quarry nearly as much (Protzen 1983: 184).

Rumiqolqa is 35 km southeast of Cuzco, considerably further than Kachiqhata is to Ollantaytambo, but near the highway connecting Cuzco to Qollasuyu. This quarry is situated around a volcanic outcrop of andesite which intruded upon the surrounding sandstone of the area (Protzen 1983:183-184). The High Quarry at Rumiqolqa provides flowbanded andesite in thin slabs. Many of these slabs are turned into tiles which are used to pave the streets of Cuzco. The East Quarry has columnar andesite and the Central Quarry has boulderlike andesite (Protzen 1983: 185).

Back at Kachiqhata, the Inca did not quarry the granite in the proper sense. They did not cut the stone from a rock face or detach it from bedrock. Instead they went through the rockfall and carefully selected blocks to be used for construction. The quarry workers minimally dressed the stone and then the stone was sent on its way to the construction site for further adjustments and a final fitting. Several blocks at the site are in a state of final dressing as they made their way to the ramps for transport. One of them has similar marks to an unfinished obelisk at Aswan in which a hammerstone was used to pound away at a piece until the desired shape was reached. Protzen found in the West Quarry at Kachiqhata a several long “needles” of gray granite. These “needles” were about 7m long with a cross section of 40cm by 40cm. He guesses that these “needles” could have been broken into smaller blocks, but there doesn’t seem to be any traces of wedges or other tool marks (Protzen 1983: 186). Locals believed the “needless” were used to construct a bride over the Urubamba, but Protzen finds this unlikely since the river is about 20m to 30m wide. The only blocks that sound remotely like the “needles” are the lintel blocks used over the doorways at Manyaraqai (Protzen 1985: 167). Ooooh, mysterious.

At Rumiqolqa you find the opposite with the andesite. The rock is broken off the face of outcrops and dug out of pits. Unfortunately this quarry has still been worked into modern times. Protzen did find an isolated section of the quarry that appeared not to have any modern work in order to do his analysis. He named it the Llama Pit after two petroglyphs found on a nearby rockface, how cute. The pit is about 100m long by 60m wide and between 15m to 20m deep. Within the pit are about 250 stones in various stages of dressing that were ready to their duty and support the Empire, but for whatever reason were never finished and used (Protzen 1983: 186). The pit contains three types of stone. The first stratum is of porous and loose material near the surface that is used commonly in regular bond masonry in Cuzco. The second stratum contains fractured and denser rocks. The bottom stratum contains the dense and large pieces of andesite. The bottom layer is still fractured, but with large pieces that pose no problems in extracting from the ground with wooden sticks (Protzen 1983: 187).

Protzen scoured the Rumiqolqa quarry for evidence of what tools were used to do all this quarrying and dressing and found it to be simple river cobbles used as hammer stones. Most of them are quartzo-feldspathic sandstones which have metamorphosed to various degrees in case you geologists were wondering. Some of them are pure quartize, granite, and olivine basalt. All of these hammers have a hardness of 5.5 on the Moh’s scale which is comparable to the andesite, but unlike the andesite, do not easily shatter and break. These hammerstones were then used to essentially flake off the block from the rock face (Protzen 1983: 188).

Being a man of science and probably having a nice grant in which to do something like this, Protzen set about testing his hypothesis using his own gathered hammerstone and a section of rockface that didn’t appear to have any previous work on it. Using a hammerstone made from metamorphosed sandstone Protzen was able to knock off a protrusion of andesite in just six blows. Using a second hammer Protzen began to pound away at a face of the block to shape it. Direct blows just crushed the surface. Small angled blows created small flakes. Blows almost 45° to the surface produced the best result with the largest flakes. Protzen also found that despite his hammer weighing 4kg, the work was not that tiring if he let gravity do a large portion of the work. If you drop the hammer and keep your hands on it to guide it, the hammer will actually bounce back from the surface of the andesite. To dress just one face it took Protzen, an unskilled mason, 20 minutes. In order to protect the finished face of a block, one must draft the edges to prevent chipping. This drafting accounts for the sunken joins commonly seen in Inca stone masonry. Most of the blocks had dihedral angles greater than 90°. Protzen was curious as to how the Inca made concave edges on some of their blocks. The answer came in the form of a long quartzite tool found at the quarry that could have been used as either a hammer or a chisel which shows wear on both the pointed and blunt ends. Evidence that Protzen is on the right track in understanding Inca masonry techniques comes from pit scars found on Inca walls. On limestone these pit scars show a whitish discoloration of the stone which is the result of a partial metamorphosis of the limestone produced by the hammer (Protzen 1983: 188-190).

What Protzen discovered about these construction blocks is that there are two kinds of joints in construction: bedding joints, the joints which most of the weight is transmitted to the course below, and the lateral or rising joints, basically the sides of the block. The “hookstones” that Bingham describes at Machu Picchu are not so much ways to keep the blocks from moving, but where two walls met from two different groups building the same wall. If Bingham was correct in saying that “such a house, whose attic was entirely above the level of the Beautiful Wall, would tend to lean away from the wall” than the “hookstones” would have done nothing to keep the wall from falling apart (Prtozen 1983: 191-192).

After examining wall constructions Protzen discovered that many of the blocks contained cuts made into the stone to receive the next block above it. This refutes the idea that the blocks were ground against each other to obtain a perfect fit. To understand how this was done Protzen did an experiment on two andesite blocks; the smaller one was used to understand the dressing process and the other larger one to understand the bedding joint process. Protzen placed the smaller block on the larger and outlined the face using the sap from a bush called llawilli which the local quarrymen use for their own work. After outlining the block Protzen pounded out the shape and used the dust produced from the process to check his work by placing the smaller block back in position and seeing where the dust was compressed. This may or may not have been a part of the Inca process, there is really no way to tell. This is ultimately a technique of trial and error and took a while for Protzen, he didn’t specify how long, and he is an unskilled stone tool using stonemason. In the hands of a skilled stonemason familiar with using stone tools the time would obviously be less. This technique allows for the close joints observed in many of the walls and takes into account the sometimes curved seams between blocks (Protzen 1983:192-193).

Rising joints are deceptive to the observer. Unlike bedding joints which are fairly even throughout the seam, rising joints are not always so consistent. Sometimes they only look like they fit together for the first few centimeters. The interior of the joint is often filled with rubble (I should note, those are two different blocks in two different walls). Harth-terré (1965) dubbed this method “wedge-stone” construction. The lateral joints were shaped in a similar way to bedding joints in that the new block was fitted into the already laid blocks with joints taken out to make it fit (Prtozen 1983: 193). Thus the 12 sided block that this has all been about may not even be truly 12 sided if you pulled it out, just the face is 12 sided. Very upsetting for a lot of readers I’m sure.

What about build order? Protzen drew a wall section with a corner from the First Rampart at Saqsawaman. What Protzen did was look at the blocks, look at how they were fitted together, and tried to determine in which order they were most likely placed. Knowing how the blocks were shaped and how the sides of the faces can be deceptive, one can piece together the building order based on the bedding joints (Protzen 1983: 193-195).

Unfortunately Protzen doesn’t discuss how the blocks were transported or lifted into place. I think I’ve read something about it or something similar for cultures that lacked draft animals, but I’m going to save that for another day. I welcome any feedback and criticism. Like I said at the beginning of this whole thing, I just wanted to summarize these articles in light of all the ignorant comments in /r/Pics.

I’ve uploaded the articles to Dropbox if anyone wants to read them.

Do ancient stone walls of Saksawwaman in Peru contain hidden communication?

Lying on the northern outskirts of the city of Cusco in Peru, lies the remarkable walled complex of Saksaywaman (Sacsayhuaman), famous for its stone walls, which display a precision of fitting that is unmatched in the Americas. This, combined with the variety of interlocking shapes, and the way the walls lean inward has puzzled scientists for decades. But there is another puzzle hidden in the stones of Saksaywaman – the angles of the stones, according to researcher Dr Derek Cunningham, correspond to astronomical alignments.

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