March-April 2004 AGGMAN Carved

Rock Stars: The Rosetta Stone

Used by scholars to solve ancient mysteries, the mystery of this rock’s origin also is finally solved.

The Rosetta Stone.

Plate tectonics, a slab of black rock, a decree to a child king, a soldier in Napoleon’s army, an 18-year-old French scholar, some black printer’s ink, and some special cleaning solution all combine to create a fascinating series of mysteries surrounding one of the most famous of all rocks. Like Archimedes’ bath or Newton’s apple, the name of this rock is instantly recognizable as an icon of an intellectual breakthrough — the Rosetta Stone.
Let’s tag along with the Rosetta Stone, starting during the latter part of its rock cycle about 25 million years ago near what is now the Red Sea. We have gone down through the lithosphere, the upper layer of the earth, and are at the boundary with the asthenosphere, the plastic layer in the earth upon which the tectonic plates move. The lithosphere generally is 60 to 125 miles thick, but at this divergent boundary, the lithosphere is only about 20 to 25 miles thick.
A divergent boundary is a place on the earth where two tectonic plates (here, the Arabian and African Plates) pull apart from one another. As the plates slowly pull apart, the overlying lithosphere thins, and cracks begin to appear. The weight of the lithosphere is reduced and so is the pressure that the lithosphere created. With this reduction in pressure, the hot rock in the asthenosphere melts into magma. The hot magma rises and squeezes through the widening cracks. It eventually cools slowly underground to form igneous intrusive rocks or flows onto the land surface and cools quickly to form igneous extrusive rocks (see “How to Identify Rocks” on p. 33). At this location, the rocks consist mostly of dark-colored iron-rich, magnesium-rich, and calcium-rich minerals and when cooled form gabbro (commonly referred to by the stone industry as black granite) or basalt (also called trap rock). The main difference between the two rocks is that gabbro is intrusive and made up of large crystals, whereas basalt is extrusive and has small crystals.
Fast forward about 25 million years to 196 BC. By now, geologic processes have pushed some of the gabbro up to the land surface and exposed it through erosion. Nearby, Ptolemy V, who was only about 5 years old, became king of the Ptolomaic Dynasty. A decree honoring the king was inscribed on a stela of hard stone to be placed in a temple of Ptolomy. That stone happened to be gabbro mined from a quarry in the desert between the Nile River and the Red Sea. To ensure that everyone could read the decree, it was carved into the stone using three scripts: Demotic, the common script of Egypt; Greek, the language of the rulers of Egypt; and hieroglyphic, the script used for religious and other important documents.
Fast forward another 2 millennia to July 1799. The stone with the decree was no longer in a holy temple; it was now part of a wall in Rashid, a small village in the Nile Delta. Part of Napoleon’s army in Rashid was tearing down the wall to make a fort when an officer and scientist, Pierre François Xavier Bouchard, discovered the stone. Europeans referred to Rashid as Rosetta; thus, the stone’s moniker — the Rosetta Stone.
The great significance of the Rosetta Stone is that it provided the key to deciphering Egyptian hieroglyphs, a long-forgotten system of writing that used pictures to represent words or sounds. Copies of the scripts were made by lithographers who covered the stone’s surface with printer’s ink, laid sheets of paper over it, and used rollers to obtain impressions. Impressions of the stone were sent to scholars throughout Europe. The Rosetta Stone was ceded to the British when the French surrendered in Egypt in 1801. It has been exhibited in the British Museum since 1802.
In 1808, French scholar Jean-François Champollion, at age 18, began working on the Rosetta Stone inscriptions. After 14 years of comparing Demotic and Greek with hieroglyphics, he deciphered the hieroglyphs. Finally, after hundreds of years of silence, ancient Egyptian writing could again be read!
For many years, the Rosetta Stone was considered to be basalt. But it was the printer’s ink used to make copies of the inscriptions and layers of oil and grime from thousands of human hands touching the stone that gave it the characteristic black, uniform color of basalt.
In 1999, the Rosetta Stone was restored before becoming the centerpiece of the Cracking Codes exhibition at The British Museum. All of the contaminants were removed except inscriptions contemporary with its acquisition (“Captured in Egypt by the British Army in 1801” recorded on the left side and “Presented by King George III” recorded on the right). A small area at the bottom left-hand corner of the stone has also been left uncleaned.
Restoration revealed a grey stone with large crystals, a natural sparkle, and a broad pinkish vein at the top. With its disguise removed it became obvious that the Rosetta Stone is gabbro, and not basalt.
The final mystery was solved!

William H. Langer is a geologist with the Mineral Resources Team of the U.S. Geological Survey.

March-April 2004 Carved in Stone Rock Stars:The Rosetta Stone				Rock Stars: The Rosetta Stone Used by scholars to solve ancient mysteries, the mystery of this rock’s origin also is finally solved. By Bill Langer The Rosetta Stone. Plate tectonics, a slab of black rock, a decree to a child king, a soldier in Napoleon’s army, an 18-year-old French scholar, some black printer’s ink, and some special cleaning solution all combine to create a fascinating series of mysteries surrounding one of the most famous of all rocks. Like Archimedes’ bath or Newton’s apple, the name of this rock is instantly recognizable as an icon of an intellectual breakthrough — the Rosetta Stone. Let’s tag along with the Rosetta Stone, starting during the latter part of its rock cycle about 25 million years ago near what is now the Red Sea. We have gone down through the lithosphere, the upper layer of the earth, and are at the boundary with the asthenosphere, the plastic layer in the earth upon which the tectonic plates move. The lithosphere generally is 60 to 125 miles thick, but at this divergent boundary, the lithosphere is only about 20 to 25 miles thick. A divergent boundary is a place on the earth where two tectonic plates (here, the Arabian and African Plates) pull apart from one another. As the plates slowly pull apart, the overlying lithosphere thins, and cracks begin to appear. The weight of the lithosphere is reduced and so is the pressure that the lithosphere created. With this reduction in pressure, the hot rock in the asthenosphere melts into magma. The hot magma rises and squeezes through the widening cracks. It eventually cools slowly underground to form igneous intrusive rocks or flows onto the land surface and cools quickly to form igneous extrusive rocks (see “How to Identify Rocks” on p. 33). At this location, the rocks consist mostly of dark-colored iron-rich, magnesium-rich, and calcium-rich minerals and when cooled form gabbro (commonly referred to by the stone industry as black granite) or basalt (also called trap rock). The main difference between the two rocks is that gabbro is intrusive and made up of large crystals, whereas basalt is extrusive and has small crystals. Fast forward about 25 million years to 196 BC. By now, geologic processes have pushed some of the gabbro up to the land surface and exposed it through erosion. Nearby, Ptolemy V, who was only about 5 years old, became king of the Ptolomaic Dynasty. A decree honoring the king was inscribed on a stela of hard stone to be placed in a temple of Ptolomy. That stone happened to be gabbro mined from a quarry in the desert between the Nile River and the Red Sea. To ensure that everyone could read the decree, it was carved into the stone using three scripts: Demotic, the common script of Egypt; Greek, the language of the rulers of Egypt; and hieroglyphic, the script used for religious and other important documents. Fast forward another 2 millennia to July 1799. The stone with the decree was no longer in a holy temple; it was now part of a wall in Rashid, a small village in the Nile Delta. Part of Napoleon’s army in Rashid was tearing down the wall to make a fort when an officer and scientist, Pierre François Xavier Bouchard, discovered the stone. Europeans referred to Rashid as Rosetta; thus, the stone’s moniker — the Rosetta Stone. The great significance of the Rosetta Stone is that it provided the key to deciphering Egyptian hieroglyphs, a long-forgotten system of writing that used pictures to represent words or sounds. Copies of the scripts were made by lithographers who covered the stone’s surface with printer’s ink, laid sheets of paper over it, and used rollers to obtain impressions. Impressions of the stone were sent to scholars throughout Europe. The Rosetta Stone was ceded to the British when the French surrendered in Egypt in 1801. It has been exhibited in the British Museum since 1802. In 1808, French scholar Jean-François Champollion, at age 18, began working on the Rosetta Stone inscriptions. After 14 years of comparing Demotic and Greek with hieroglyphics, he deciphered the hieroglyphs. Finally, after hundreds of years of silence, ancient Egyptian writing could again be read! For many years, the Rosetta Stone was considered to be basalt. But it was the printer’s ink used to make copies of the inscriptions and layers of oil and grime from thousands of human hands touching the stone that gave it the characteristic black, uniform color of basalt. In 1999, the Rosetta Stone was restored before becoming the centerpiece of the Cracking Codes exhibition at The British Museum. All of the contaminants were removed except inscriptions contemporary with its acquisition (“Captured in Egypt by the British Army in 1801” recorded on the left side and “Presented by King George III” recorded on the right). A small area at the bottom left-hand corner of the stone has also been left uncleaned. Restoration revealed a grey stone with large crystals, a natural sparkle, and a broad pinkish vein at the top. With its disguise removed it became obvious that the Rosetta Stone is gabbro, and not basalt. The final mystery was solved! William H. Langer is a geologist with the Mineral Resources Team of the U.S. Geological Survey.