The Ulu: Chemistry and Inuit women’s culture

The Ulu 

What is an ulu? An ulu1 is a multi-purpose cutting tool with a semi-circular blade and a handle. It has been a major part of an Inuit woman’s life and culture for at least the last 4500 years. The ulu has a great advantage over a conventional knife, as a physicist or kinesiologist would tell you. With an ulu, one is pressing directly down, providing the most efficient force, while a standard knife is held at right-angles to the direction of applied force and at a distance from the cutting blade.

a semicircular metal blade and a wooden handle -- ulu

a semicircular metal blade and a wooden handle -- uluFigure 1. The two Andersen family ulok: (top) Chaim’s paternal grandmother’s; (bottom) Chaim’s mother’s maternal grandmother’s. (credit: Chaim Andersen)

Using knowledge and skills passed down from generation to generation, women use the ulu for such things as cleaning skins, cutting up meat for food sharing, filleting fish, making clothes, cutting a child’s hair, trimming blocks of snow (see later article in this series) and for a wide range of communal activities. This tool is so central to Inuit life that the same word “ulu” is used for it in the diverse languages and dialects of northern peoples all the way from the Russian Aleut, to the Alaska Yupik, across the various groups of northern Canadian Inuit, to the western Greenland Inuit. Using an ulu is one of the ways that Inuit women connect to Inuit culture as well as give back to it, while the ulu itself is a unique implement which makes Inuit culture and traditions very rich and very much alive. 

Chaim Andersen: the ulu and an Inuit woman’s identity

In Inuit tradition, it is considered an honour to receive an ulu from an older female relative. My mom was given two ulok (Inuttitut for two ulu): one from my ânak (paternal grandmother); and the other from her anânsiak (maternal grandmother). To clean animal skins, my mom would use the ulu given to her by her anânsiak. Though she values my ânak’s ulu greatly, she feels more pride in using something that was given to her by someone who played such an important role in her childhood years. So she uses her anânsiak’s ulu more often, and it is evident in the size of the blade (the more you use it, the more it needs sharpening; the more you sharpen, the smaller the blade gets). In Figure 1, the reader can see both ulok that, to this day, are still stored in the exact spot they’ve always been displayed: above the stove.  

Chaim Andersen’s ulu reminiscences

As a child, I always remember being told never to touch the two ulok that were stuck up above the kitchen stove, where my mom had dug them into the crevasses of the cupboards and the wall. She has always had them there, where they could remain untouched, where risk of damage was low and preservation was optimal. However, on some days, my siblings and I would come home from school to see her in the middle of the living room hunched over, cleaning a seal skin (Kisiligek — to clean a seal skin). The skin was given to her by a family member who had been hunting the previous day. Sometimes, when she would clean two, maybe three skins in the duration of two whole days, our house would smell of seal fat for what felt like weeks. And I knew she would come and ask me to stretch the skin with her — which, I might add, if you’re not used to it, causes your hands to turn into jelly from trying to grasp onto the slippery skin while pulling it tight. But I was always so proud to be her daughter in those moments, and I remember thinking “One day, I’m going to do that with my daughter.”

Along with the smell of seal fat, the tired hands and the pride of being a little Inuk girl, I remember asking frequently: “Mom, can I try?” to try to get her permission to help her clean the skin. My mom, with her perfectionistic qualities (positively speaking), no matter how bothered she was with my frequent interruptions, would always answer with “no, you’re going to ruin it.” At first, I figured how hard could it be? After all, I’ve watched her time and time again clean a seal skin without flaw. How naïve I was! In the summer of 2018, I finally found the time, had the skin, and with the same ulu my mom uses, I had the privilege of cleaning my first one. It took me five to six hours! I cut through the skin up to ten times, and in some parts, I left a bit too much fat. Let’s just say, my first time was unsuccessful. It takes extreme precision, immense patience, muscular strength, and the inherited knowledge of Inuit women to skillfully clean a seal skin with an ulu. Over time, it becomes second nature to do so, and it is a skill that Inuit women must retain in order to honour their female ancestors.

Chaim Andersen cleaning a seal skin with an ulu

Figure 2. Chaim Andersen, Summer 2018, allowed for the first time to clean a seal skin using one of the family ulu. (Credit: Chesley Ittulak)

Ulu chemistry

The handle of an ulu has usually been wood, bone, or ivory; three of the composite materials used by the Inuit (see a subsequent part of this series). In this article, we will focus upon the materials used for the blade. Of the surviving historic uluit (Inuttitut for more than two ulu), slate has been the most widely-used blade material, but as we discuss below, always inventive, where available, the Arctic peoples have long used both iron and copper for this purpose.

Slate-bladed ulu

In a previous part of this series,2 we described how the chert deposits in Ramah Bay were used by early Indigenous peoples to manufacture cutting implements. Chert, almost pure silicon dioxide, has a network covalent structure. When a piece of chert is struck hard by a stone, flakes fracture off (called conchoidal fractures), leaving an uneven, serrated edge to the tool.

Inuit preferred slate for their sharp-edged tools, including the ulu. Slate3 is a very different mineral from chert. Slate has a layer-structure enabling thin sheets to be cleaved off, providing a smooth-surfaced tool which can be ground (and re-ground) to a sharp edge. With a wood, bone, or ivory handle, the slate ulu (Figure 3) was a very proficient tool for its many uses.

a semicircular metal blade and a bone handle -- uluFigure 3. Ancient slate-bladed ulu, several hundred years old.
(Credit: Newfoundland Heritage, by permission)

Why does slate have this layered structure? Slate was formed in seas from clay and volcanic ash deposits. Buried under millions of years of deposit and subject to heat from the Earth’s interior, a series of chemical changes occurred, known as metamorphism. The strong compression caused the ions to reassemble as different minerals with the crystals spreading in the planes at right angles to the compression direction. Thus the sheet nature of slate is reflective of the molecular/ionic structure.

The composition of any particular slate depends upon the chemical composition of the clay but an approximate generic formula can be written as: (K)(Al,Mg,Fe)2(Si,Al)4(O)10(OH)2. This formula looks very intimidating, but the structure is reasonably simple (Figure 4). There are layers of joined tetrahedra with Si4+ ions at the centre, surrounded by four O2− ions. Then there are joined octahedra with Al3+ at the centre, surrounded by six O2− ions. The large K+ cations, combinations of the small Al3+, Mg2+, Fe3+ cations, and large OH anions then fit in spaces in between and balance the charges to make the mineral electrically-neutral. It is the gaps between the layers (shown on the figure where the star-shaped cations and water molecules are located) that provide the horizontal cleavage characteristic of slate.

a molecular model of the atoms inside a clay mineral showing metal atoms between layering of silica sheetsFigure 4. Typical structure of a clay mineral with the corresponding key. From:

Iron-bladed ulu

In addition to slate-bladed uluit, there were once iron-bladed ulu which did not have a European origin. How could the Inuit have had iron metal when, in their environment, iron-smelting would have been impossible? The answer lies in Greenland.

About 5,000 years ago, a massive meteorite crashed into western Greenland.4 After impact, causing a 30 km diameter crater, some of the ejected meteorite fragments fell at Cape York near Savissivik, Meteorite Island, Greenland. The more precise chemical composition of themeteorite is 92.3% iron, 7.6% nickel and traces of other elements. Uniquely, embedded among the alloy crystals, there are crystals of chromium(III) nitride, CrN (Figure 5).

1 ratio of chromium to nitrogen is shownFigure 5. The packing arrangement in chromium nitride (chromium-silver; nitrogen-blue) from: 

To account for the metallic composition, we must assume that the meteorite had once been part of the core of a primeval planetoid large enough and hot enough to have a molten metal core. A subsequent collision with another large body would have resulted in large chunks hurtling through space, this meteorite having been one of them.

As no other meteorite on Earth contains this mineral, iron artifacts can be conclusively identified as having come from the meteorite. From about the mid-eighth century, the Indigenous people used iron from the meteorite to manufacture blades for both harpoons and uluit. The archeologist, V. F. Buchwald has commented:

Small meteorite fragments in situ are rarely reported because the Inuit for centuries with their unerring and keen observance long since have collected all that was available. … The small fragments were useful because they, on cold working, could be shaped into lanceheads, knives and ulus.5

This cold-working required the use of basalt rocks as hammer stones (the igneous silicate-rich basalt is about 6 on the Mohs hardness scale while iron is about 4 to 5). Not only did the Greenland Inuit prize iron-bladed tools (including uluit) (Figure 6) but iron from this meteorite has been found across northern Canada.6 Artifacts (including uluit) made with Cape York meteoritic iron have been found on Ellesmere Island and Somerset Island in northern Canada. There have even been Greenland meteoritic iron objects found south of Hudson Bay, 2400 km from the Cape York meteorite site, implying the existence of elaborate trade networks.7

In more modern times, contact with European explorers and settlers provided a new source of iron. For example, by the 1600s, Inuit were acquiring iron from European fisher-people on the north-east coast of Canada. An iron ulu from an abandoned Inuit settlement on the Labrador coast has been dated back to that very early period of European settlement.8 

Copper-bladed ulu

During the spring of 1851, a British expedition to the Arctic on the ship Investigator encountered the Inuit of Victoria Island (now part of the Northwest Territories). Much to the crew’s amazement, copper was being used for artifacts (including uluit). The captain, Robert McClure, commented:

… their knives, arrows, needles, and other cutting and piercing instruments were all made of copper … fashioned into shape entirely by hammering. No igneous power [smelting] being had recourse to, it was surprising to see the admirable nature of the work, considering the means by which it was effected, and the form reflected great credit on their ingenuity and excellence in the adaptation of design.9

an ancient rusted iron-bladed uluFigure 6. Ancient (meteoritic?) rusted iron-bladed ulu (Credit: National Museum of Greenland collection) 

These Indigenous peoples were using lumps of naturally-occurring malleable copper metal found on the bare rocky surface. The copper had not oxidized, even over millennia. This should come as no surprise to a chemistry student, as copper is near the bottom of the Reactivity (or Activity) series, just above silver and gold of the common metals.10 In the archaeological explorations of the Victoria Island region, copper ulu blades were found to be quite common (Figure 7).11

a semicircular copper blade and a bone handle -- uluFigure 7. Copper-bladed ulu from the copper Inuit region made between 1800 & 1850 (British Museum collection).15 

Called the Northern Copper Inuit12 by Europeans, in recent times the peoples have been centrally-resettled on Victoria Island at a place the Inuit have named Ulukhaktok.13 The name of the community, Ulukhaktok, means “the place where ulu parts are found” in the local Kangiryuarmiutun dialect, signifying the importance of the ulu in Inuit life.

The question arises: “How can we be sure an artifact was made from the free element rather than from copper hull-sheathing of abandoned European explorer ships?” Actually, there are two ways. First, the metal crystal grain size is much larger for the free-element copper. This is because the liquid copper, embedded in rock magma, cooled slowly. Smelted copper, on the other hand, cooled very quickly, resulting in small grain size. But there is an even more precise technique: that of elemental analysis. The free copper on Victoria Island was found to be of very high copper purity, while smelted European-source copper contained significant concentrations of arsenic, antimony, nickel and selenium.14

From Inuit tool to kitchen must-have

The design of the ulu as the perfect cutting instrument has led it to become a must-have modern kitchen implement. For example, Amazon Inc.™ lists several pages of different commercially-manufactured uluit, all with steel blades but with every possible handle-material from birchwood to caribou antler to silicone rubber.

Student questions

  1. In the structure of slate, the potassium ion is said to be ‘large’ and the aluminum ion ‘small’. The radius of a potassium ion is 152 pm and that of an aluminum ion is 67.5 pm. How much bigger in volume is the potassium ion than the aluminum ion? (volume = 4/3 π r3)
  2. Many copper-bladed ulu have survived. Why are there so few surviving iron-bladed ulu?
  3. It is not clear whether chromium nitride is an ionic compound or metallic with nitrogen atoms in the spaces. 
    (i) If it is ionic, what would be the charge on the chromium ion, and hence the correct name?
    (ii) The distance between the chromium and nitrogen centres is about 206 pm. If it is ionic, the chromium ion has a radius of 65 pm and the nitride ion, 140 pm. Look up the atomic radii of the two elements. If the structure is metallic, what should the Cr to N distance be? Does that help us distinguish the two possibilities?


We think it fitting to dedicate this article to the Inuit women who have used their skills with the ulu to contribute to the survival of their people in such a challenging environment for countless generations. 

References and footnotes

1., 3., 10.;;

2.  C.C. Andersen and G. Rayner-Canham, Ramah Bay 7,000 years of Aboriginal culture — and chemistry, September 2018 

4.  P. Voosen, “Ice Age Impact: A large asteroid struck Greenland in the time of humans. How did it affect the planet?” Science, 2018, 362, pages 738-742.

5.  V.F. Buchwald, Ancient Iron and Slags in Greenland, Danish Polar Centre, Copenhagen, 2001, page 56.

6.  A. P. McCartney and D.J. Mack, “Iron utilization by Thule Eskimos of Central Canada,” American Antiquity, 1973, 38, pages 328-339.

7.  H. Pringle, “New Respect for Metal’s Role in Ancient Arctic Cultures,” Science, 1997, 277, pages 766-767.

8.  R.H. Jordan, “Archeological Investigations into the Labrador Eskimo History of Hamilton Inlet,” Them Days, 1976, 2(1), pages 20-26.

9.  A. Armstrong, A Personal Narrative of the Discovery of the Northwest Passage, Hurst and Blackett, London, 1857, pages 339-340. 

11. D.A. Morrison, “Thule and Historic Copper Use in the Copper Inuit Area,” American Antiquity, 1987, 52, pages 3-12.

12.  R.G. Condon, The Northern Copper Inuit: A History, University of Oklahoma Press, Norman, Oklahoma, 1996.

13.  The Inuit communities are spread across the thousands of kilometres of the northern coastline of Canada. As a result, in each part, the Inuit have specific names for their own location identities (ending with –miut) together with their own local dialects and traditions. Thus the so-called ‘northern Copper Inuit’ now call themselves the Ulukhaktokmiut.

14.  M.L. Wayman, et al., “The Analysis of Copper Artifacts of the Copper Inuit.” Journal of Archaeological Science, 1985, 12, pages 367-375.


About the authors

Ms. Chaim Christiana Andersen, Inuk of the Nunatsiavummiut, is currently an undergraduate student in the Environmental Science (Chemistry) program at the Grenfell Campus of Memorial University, Corner Brook, Newfoundland. Dr. Geoff Rayner-Canham is Professor of Chemistry at the Grenfell Campus.