Monday, August 17, 2009

How To Get A Round Rock

My aunt Marlene left this morning on a 5 am flight bound for Regina via Toronto. Uncle Gary booked later and couldn't get the same flights, so he's with us until Tuesday evening. They rented a car over the weekend and toured around the Irish Loop and some of the Baccalieu Trail.

Lori and I had a pretty quiet weekend at home. I worked a little on two stone ball reproductions from the collection of artifacts from Ivvavik National Park. The original artifact is pretty close to a perfect sphere and is about 3.5 cm in diameter. It was found in a historic site alongside other toys. Without scratching it or cutting into it its pretty hard to identify the material. It could be clay or stone. I've shown the object to archaeologists and potters and opinions are split. Parks Canada showed this object and the others from Ivvavik National Park to Inuvialuit elders and the majority identified it as a round stone similar to others that they had seen within the area. I'm more comfortable working with stone, so I've chosen to make the reproductions from limestone that I picked up on the west coast of Newfoundland. The weathered surface of the stone is very similar to the weathered surface of the Ivvavik artifact.

I carve the stones into a sphere using my angle grinder with a diamond cutting blade and then tumble them in a rock tumbler for a couple days to erase the tool marks and wear down the facets. The secret to grinding a sphere out of rock is to look for the sharpest angles and grind them down blunt. Keep turning the rock looking for the sharpest angles. Unfortunately the natural weathered surface of the stone is worn off almost immediately and I need to antique the surface to recreate that worn cortex. To add the cortex I use a combination of red ochre, soapstone and limestone dust, diluted carpenters glue and a blow torch. I'm working towards a dusty texture and a warm yellowish-buff-brown colour. I made one of these for Parks last year and I know that I can get a pretty good match to the artifact if I keep adding lots and lots of very thin layers. I'll compare the progress so far to the artifact during my Rooms visit on Tuesday.

The limestone spheres immedietly after carving with the angle grinder and diamond blade.

The same rocks after 36 hours in the rock tumbler.

After the first pass of antiquing. The ball in the foreground is getting close, but I think I may need to tone down the ochre colour in the one in the back.

Photo Credits: Tim Rast

Photo Captions:
Top: The Ivvavik stone ball artifact
Second: My rock tumbler - purchased a couple years back at Toys R Us
Third-Fifth: Stages of stone ball manufacture.


  1. Wow, your rock tumbler is so . . . plastic. You need one of these:

  2. When this one wears out I might look for an upgrade. I wouldn't mind finding something a little quieter, but for the amount I use it, I think this one will be with me for a while.

  3. I'm not sure they come in quieter. I have to put mine off in the back of the house and away from normal living space.

  4. how on earth do you grind the rocks without grinding your hand? Do you use a jig or some other tool to hold your rocks? Mine keep rolling in my hand, very dangerous.

  5. Gloves are important. If your grinder is too heavy to easily hold with one hand, its best to hold the grinder stationary and grind the rock against it.

  6. Mary Lynn E. LongsworthJuly 22, 2011 at 12:07 PM

    How much did the marble weigh? Depending on the site, a fair amount of the historic spheres (toy marbles) are coming out of Germany, and the plain gray ones tend to be undecorated ceramics. Stone marbles certainly were made, though what I've run across are primarily the brightly colored stones such as agates. I've found in my research that the stones weigh more than the ceramics, but limestones and such have been hard for me to get my hands on to analyze locally; we're just not finding them in the historic sites in St. Louis. Possibly it's because we did not have marble factories locally (that I'm aware of), and a LOT of trade with Germany; St. Louis had a heavy influx of German immigrants.

    Would love to hear more on the historic toys of Ivvavik! (marylynn.e.longsworth (at)

  7. Thanks Mary Lynn - I sent the sphere back to Parks Canada when I was done with it so I'm afraid I can't help with the weight question. That's interesting about the marbles - I didn't know about their history.

  8. Hiking in the hills today I found a round rock. I wonder if it's real. I live in northern California.


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