Emery

In short

Emery is a black or dark grey, granular, heavy rock in which corundum, a very hard mineral, is mixed with iron minerals such as magnetite, hematite and spinel. It has been used since antiquity to grind and polish stone, metal and glass. Because it is a rock rather than a mineral, its hardness varies with the mix, from about 6 to 9. With its deposits in the Aegean, Türkiye is one of the world's main producers.

Photos

How to recognise it

1. 1

   It is a black or dark grey, granular, compact rock that feels clearly heavier than an ordinary stone of the same size (specific gravity about 3.5–3.8).

2. 2

   Corundum-rich pieces are very hard and scratch quartz and glass. Hardness falls as softer minerals are mixed in and can drop as low as 6.

3. 3

   Pieces rich in magnetite may attract a magnet. A survey of an emery field in Muğla found that the rocks produce measurable magnetic anomalies.

4. 4

   It is not always easy to tell from black basalt, hematite or magnetite by eye; a sure identification needs a microscope or X-ray diffraction.

Myths and misconceptions

• MythThe “emery stone” (grinding wheel) in a workshop is a natural stone.

  FactIn Türkiye a grinding wheel is called a “zımpara taşı” (emery stone), but most are made by bonding synthetic abrasive grains (aluminium oxide, silicon carbide, diamond or cubic boron nitride) with a binder such as ceramic, bakelite or rubber.

• MythSandpaper is made of emery.

  FactMost sandpaper today uses synthetic aluminium oxide or silicon carbide. According to Britannica, emery has been largely replaced by synthetic abrasives in sandpapers; Wikipedia lists it mainly for metal polishing.

• MythEmery and corundum are the same thing.

  FactCorundum is the mineral aluminium oxide. Emery is a dark rock in which corundum is mixed with iron minerals such as magnetite, hematite and spinel, so its hardness can be lower than that of pure corundum (9). Gem-quality corundum is ruby and sapphire.

Did you know?

Where is it found?

• Koronos–Apeiranthos area, Naxos, Greece · Historic sourceThe Aegean's most famous emery source; the island exported its emery to other islands as early as the Neolithic. According to the Samos study, the right to mine it belongs to the villagers of Apeiranthos and Koronos.
• Mikri Lakka, Samos, Greece · Known localityEast of Vathy; diaspore-rich emery of lower quality than Naxos. About 5,000 tons were mined in 1906–1914 and sold to France, Germany, Austria and the USA; the mines were soon abandoned. The point is the position of the old quarries.
• Ikaria, Greece · Known localityAccording to the Samos study, emery also occurs on Herakleia, Sikinos, Ios, Paros and Ikaria besides Naxos and Samos. The point is the general position of the island.
• Peekskill area (Cortlandt), New York, USA · Major depositAccording to Britannica this is where emery was most worked in the United States; a 1944 report says the country's domestic emery output in 1936–1942 came entirely from the Peekskill area. The point is the position of the city of Peekskill.
• Chester, Massachusetts, USA · Historic sourceThe emery vein was found in 1864 and worked at once to supply the Northern arsenals with abrasive during the American Civil War; the mines closed in 1913. The vein is about 6 km long.
• Karacasu, Aydın, Türkiye · Major depositThe Göztepe and Bölükardıç deposits at Karacasu were being worked as of 2019; the ore grades 55–60% Al₂O₃ and measured plus probable reserves were put at about 172,000 tons. The point is the position of the district town of Karacasu.
• Söke (Gümüşdağı, Kemer, Kayas Farm), Aydın, Türkiye · Historic sourceIn Ottoman times the emery mines at Gümüşdağı and Kemer farm in Söke were the subject of mining concessions. The known sites today (Gümüşköy, Kayas Farm) are abandoned; the ore grades 44–55% Al₂O₃ and probable reserves are about 55,000 tons. The point is the position of the district town of Söke.
• Kayabaşı village area, Milas, Muğla, Türkiye · Known localityNear Kayabaşı village south of Milas lies an iron-rich emery ore field with a measurable magnetic signature, studied with geophysical surveys. The point is the position of the district town of Milas.
• Mt. İsmail, Yatağan, Muğla, Türkiye · Known localityAbout 15 km northeast of Yatağan, lenses of corundum-rich metabauxite 1–5 m thick, extending about 3 km within Late Cretaceous marbles. The point is the position of the district town of Yatağan.

Locations are approximate to protect sites. Red dots mark places in Türkiye. Open in the big map →