This article explains the scientific value of measurements when it comes to stone. In short the MOH value is not the defining determination of hardness or susceptibility to cutting or chipping.
The Giza Building Project
Their is also a huge logical fallacy on your part using this argument. If copper chisels could not have cut into limestone then they could not have carved any of the inscriptions in any limestone block. Therefore all inscriptions on all monuments would have existed only during the bronze age or later since bronze is hard enough to carve limestone. Or that there is a mysterious tool made of unknown material that no one has ever found was used to carved the inscriptions. Do you realize how ridiculous this sounds?
This video shows a copper chisel cutting limestone and even flint shaving limestone:
what the ancients knew I Shorts: Stone Cutting Tools : Video : Science Channel
This video shows a copper tube cutting granite:
what the ancients knew I Shorts: Egyptian Drill : Video : Science Channel
It's a similar technique that Chris Dunn demonstrated on Ancient Aliens.
The fact that Romans did successfully transport several hundred ton obelisks across the Mediterranean proves that it can be done. Whether their specific techniques were identical is debatable but being able to demonstrate that massive stones can be moved and erected by water transportation in ancient times is a given. You said it was impossible. It is easy to just say the large barges didn't exist but you can't prove that. You simple ignore the carvings showing barges carrying obelisks as just "a depiction" and the writings from an eyewitness. How convenient.
There is indication from carbon dating that the Egyptians did indeed deplete there forests of old growth wood needed in the construction of the pyramids and the barges. This may explain why future construction projects were never as big. There are historical precedence of people depleting forests for construction or industrialization. It happened at Easter Island and it happened throughout Europe in the modern era.
I find it strange that people expect a lot of documentation of structures that are built several thousand years ago. I can't even find the blueprints of a 10 year old remodel at city hall. After such a long period a host of things could have happened that would have destroyed any such evidence assuming it was even kept. Wars, natural dissasters, fire, jealous Pharoahs, religious upheaval, and so on could have caused important documents to be destroyed. Never mind that after several thousand years any kind of documents written on papyrus would even stay intact. Again there are historical precedence of important documents being destroyed both deliberately and accidentally. Like I said before the ancient Great Library of Alexandria was completed destroyed. It could very well have had written accounts of exactly how things were done. We'll never know. Book burnings in Europe were quite popular in the Medieval era. The Spaniard did an excellent job of nearly wiping out the entire library of books that the Mayans kept.
If we werer to assume that the pyramids were graves with treasures then why would we expect blueprints or any document detailing the construction? This would only help grave robbers and future pharaohs who were more than eager to replenish their treasurys with plundered goods. This could have been the reason why latter kings had their tombs hidden underground.
The one key piece of evidence that alternative theorists like to dismiss is the written inscriptions on the stone blocks above the King's Chamber that identify the pyramid as Kufus. They've been dismissed as hoaxes. However closer examination reveals that these markings by workers run under and in between the massive stones. It is definitive proof that this is Kufus pyramid.
Finally, Graham Hancock a noted author of many books that put forth alternative theories to the pyramid construction retracted his assertions that the markings on the blocks could be fake. He was given a lengthy examination of the chamber and the markings under powerful lights by the Egyptian authorities and has since recanted the hoax claim. He was able to see the marking between gaps in between some of the stones.
Here is his statement from his own webstie:
The Official Graham Hancock Website: Feature Articles
In short: "... in December 1997, Dr Zahi Hawass allowed me to spend an entire day exploring these chambers. There were no restrictions on where I looked and I had ample time to examine the hieroglyphs closely, under powerful lights. Cracks in some of the joints reveal hieroglyphs set far back into the masonry. No 'forger' could possibly have reached in there after the blocks had been set in place - blocks, I should add, that weigh tens of tons each and that are immovably interlinked with one another. The only reasonable conclusion is the one which orthodox Egyptologists have already long held - namely that the hieroglyphs are genuine Old Kingdom graffiti and that they were daubed on the blocks before construction began..."
Like many other authors of alternative theories Hancock had never been inside this chamber before he wrote his books yet made wild assertions of fraud in order to dismiss accepted theories.
