This turned up in my Tumblr dash yesterday.

I work at a state park where we have some rather large grindstones/kettlestones set up around our visitor center. I get this question almost every day from 70 year old elderly folks, to 40 year old parents, to 5 year old children, even though we have giant posters explaining that they are very round rocks that helped carve out our potholes/kettleholes years ago.


I cannot find any reference to the word "kettlestone" beyond Kettlestone, England.

So, my question is

  1. Is "kettlestone" an accepted word with an accepted definition?

What my research has turned up:

  • I've searched multiple dictionaries, Wikipedia, and etymonline.com and have found no reference to this word.
  • I did find kettle hole. A kettle hole is a shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters, according to Wikipedia. This suggests that a kettlestone is a naturally occurring stone which digs out the hole.

As a tacked on question: Can a grindstone be a natural formation? My definitions say no, but combining it with kettlestone is confusing.

  • There are many google results for "kettle stone" that are just what you've described. Commented Aug 4, 2015 at 15:38
  • @Mr.ShinyandNew安宇 Can I asked how you searched? Searching "kettle stone" in quotes finally got me pictures (I freely admit to using a single word in my research), but the entire first page of results (with and without quotes) is towns named Kettlestone or Kettle Stone and the Kettle & Stone Brewing Company.
    – VampDuc
    Commented Aug 4, 2015 at 16:12
  • Sorry, I should have written "kettle stones" which does bring back geological results Commented Aug 4, 2015 at 16:25
  • @Mr.ShinyandNew安宇 What a difference an "s" makes! I'm still confused why I couldn't/can't find an actual definition, though.
    – VampDuc
    Commented Aug 4, 2015 at 16:43
  • My understanding is that in some circumstances you have a situation where a stone sitting atop a larger piece of rock manages, over decades or perhaps centuries, to wear a depression (kettle) in the rock supporting it. This happens because water movement causes the stone to move around, but is not forceful enough to push the stone off of its supporting rock.
    – Hot Licks
    Commented Aug 6, 2015 at 12:11

2 Answers 2


Try kettle stones - two words. There's a great write-up on the site for Kettle Stones Provincial Park in Manitoba, Canada. Explains in detail and with illustrations how they were formed and more information about them.


"Kettle Stones"

"The kettle stones' long development spans millions of years. Scientists believe that the stones formed in three stages beginning in the Cretaceous Period, between 70 - 135 million years ago. The first stage took place near the shore of a shallow sea that covered the area during the late Cretaceous Period. Sand from rivers and shoreline erosion, and other marine sediments, were deposited in horizontal layers on the seabed which through time became a stratum (layer) of sandstone." (Figure 1.1). "Known as the Swan River Formation (SRF), this stratum is 100 m (metres) thick in places." Figure 1 Figure 1.1: "70-135 million years ago: Swan River Formation (SRF) sand and clay deposited in a shallow sea."

Figure 2 Figure 1.2: "1-70 million years ago: Sandstone concretions formed by chemical precipitation of calcium carbonate."

Figure 3 Figure 1.3: "8,500 years ago: Sandstone concretions emerge from surrounding Swan River Formation (SRF) by Lake Agassiz wave action and Lake Agassiz sand (LAS) was deposited."

Figure 4 Figure 1.4: "Present surface: Following the drainage of Lake Agassiz the land surface emerged and was colonized by vegetation."

Figure 1: "Formation and emergence of the kettle stones, based on concepts suggested by Gaywood Matile, Manitoba Geological Survey."

"During the second stage, regional uplift raised the stratum above the level of the sea. At this time, percolating groundwater cemented loose bits of sand and sediment together to form concretions (Figure 1.2). Sand was cemented around a nucleus or centre-an unknown base, possibly a fossil. The "glue" or adhesive was a lime solution, derived from the calcium carbonate of sea animal skeletons. In this process called chemical precipitation, the concretions maintained the layered appearance found in the original stratum."

"In the third and final stage-about 8,500 years ago-glacial ice of the last Ice Age had retreated into northern Manitoba. Lake Agassiz modified the land to look much like it does today. During the final drainage of Lake Agassiz, beaches, offshore bars and spits formed where the kettle stones were held in the soft sandstone. Waves crashed against the sandstone shore and eroded the loose material around them (Figure 1.3). The harder concretions or kettle stones were left behind with Lake Agassiz sand (LAS). Being firm and round, the stones weren't noticeably altered by the waves. Since then, wind, rain, heat and cold have weathered those that are above ground level. Some appear to be partly above the ground surface and an unknown number of others may be still completely buried (Figure 1.4). The remaining original sandstone stratum is about 10 m below the present sandy surface and extends through all of southwestern Manitoba."

"Wave erosion by Lake Agassiz has left a unique landscape, with the kettle stones propped up like sentinels overlooking the Manitoba Lowlands to the east. While the origin of the name kettles is unknown, it is generally believed that they are so named because they resemble household kettles or kettle drums."

You'll have to visit the site to see the photos and diagrams and further info.

  • 1
    Since the softer sandstone around the kettle stones (concretions) gradually washed away over time, they themselves did not actually erode or "carve out" anything. (I can best picture them as forming like [stone] pearls.) Thus a "kettle hole" is sort of a misnomer. And other than their common component of sandstone, grindstones and kettle stones are not one-and-the-same. So I agree with you that combining "grindstone" with "kettle stone" is confusing, as they aren't really interchangeable. – W9WBH 18 mins ago
    – W9WBH
    Commented Aug 6, 2015 at 15:41

In Switzerland a few decades ago I saw a number of spherical stones a foot or so in diameter called “kettle stones”, some still in pot-shaped cavities in the bedrock about 4 or 5 feet in diameter. These were formed by the rapidly flowing streams of glacial meltwater causing large rocks to rotate in niches of bedrock, grinding both the “kettle” and the contained boulder into the kettle and the contained spherical stone. Hence kettlestone. Ohio also has a history of glaciation and of rapid melting/rapid water flow, conditions which could make our own kesselsteins.

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