olelog

Why did euxinic and Trondhjemite make me think of Syenite? - (Old) place names in geological terms!

What we today call Aswan, the Ancient Egyptians called Swen or Swenet. The Copts called it Souan, probably meaning ‘trade’ (or ‘market’), but I have heard other explanations. Swenet is supposed to have derived its name from an Egyptian goddess with the same name. The Greek called the place Syene – and some of you may remember a city called Syene or Seveneh in the Bible and described as the southern limit of Egypt. I have shown the name in hieroglyphs, Arabic and Greek.

Most of the granite used in the ancient Egyptian tombs, temples and obelisks came from the quarries in the Aswan area. The granites were transported via the Nile to many important sites such as Karnak, Luxor Temple, Giza and Edfu, In fact both monumental “red” (pinkish) and monumental “black” (hornblende) granites were quarried there. - Granites can be pink because they contain pink (hematite-pigmented) (alkali) feldspars like orthoclase - Tourists can still visit an old quarry from that time (I did several years ago), and they can see an unfinished obelisk (see picture), the largest known ancient obelisk, which unfortunately developed a flaw during quarrying before they got it out in one piece (the obelisks at Karnak were all in one piece - as large as 36 m tall and some weighed more than 300 tons).

You do not have to go to Egypt to see one of the great Egyptian granite obelisks. London, Paris, Rome and New York each have one, but that is another story (From rather doubtful sources I have been told that Josephine's parting words to Napoleon Bonaparte before he left for Egypt in 1798 were: "Good-by darling! If you go to Thebes, do send me a little obelisk." In vain it seems, because Paris had to “wait” until 1831 before it got its Egyptian obelisk (made of pink Aswan granite), many years after Napoleon had met his Waterloo, a few kilometres from my place).

Syenite is a coarse-grained intrusive igneous rock of nearly same composition as granite but with no or less quartz (<5%). The term syenite was originally applied to hornblende granite like that of Aswan, and the name is derived from the Greek version of the place name (Syene). The Aswan granite is funny enough, however, no longer considered a syenite.

The name trondhjemite was given to a certain type of white granite-like rock by Viktor M. Goldschmidt in 1916. Trondhjemite is a leucocratic (light-colored) intrusive igneous rock. It is a variety of tonalite in which the plagioclase is mostly in the form of oligoclase. Trondhjemites are sometimes known as plagiogranites. He chose this name because the rocks he described were from the Trondhjem area (the city of Trondheim was called "Trondhjem" until it was changed to "Nidaros" in 1930 and "Trondheim" in 1931). In fact the city was originally given the name Kaupangen (English: Marketplace) by king Olav Tryggvason. It was for a long time called Nidaros (English: Mouth of the river Nid). In the late Middle Ages the name was changed to Trondheim. In the Dano-Norwegian period (1537–1814), during the years as a provincial town in the united kingdoms of Denmark-Norway, the city name was spelled Trondhjem. The words heim(r) (Norwegian) and hjem (Danish) all mean home, the word Trond is a tribal name, i.e. Home of the Trønders.