January 2022, Stone of the Day #6 – Petrified Wood from a Kakanui Beach

I’m not sure when I found this stone at Kakanui, just south of Oamaru in North Otago. It is one of maybe eight to ten pieces of petrified wood I have found there over the last 18 months. It’s an unusual shape but has tumble-polished quite well. It feels very smooth on the two large sides though close-up photos have revealed some tiny rough patches.

The stone is 4 cms long by 2.5 cms at its widest and 1 cm deep. Photos of the other side and of the concave edge which seems to have escaped the full effects of tumbling, being a little rougher as a result :

This stone was tumble-polished in a 3lb barrel for 14 days in tin oxide tumble polish, followed by three days burnishing tumble in borax. The barrel contained Kakanui stones that had mainly had 14 days in 600 grit first. But I needed some more to fill the barrel to the two-thirds level. Stone #6 was one of nine added that had previously undergone only a 400 grit tumble. I took a photo of the nine so I could identify them later to see if there was much of a difference in their polishing (and I couldn’t detect any, though remember that I had previously decided that the nine were smooth enough to go directly to tumble polish). Note that this photo was taken inside, in a dim room – this accounts for the dark colour of Stone #6:

The nine stones previously tumbled only in 400 grit.

Stone #6 before going into tumble polish.

There were three other pieces of Kakanui petrified wood that were tumbled in the same 3lb barrel – the middle one failed to take any shine at all, despite having a pre-polish tumble in 600 grit (this happens with petrified wood from time to time):

Three other Kakanui petrified wood stones polished in the same barrel.

This one did not shine at all!

Finally, three other examples of Kakanui petrified wood, these ones having been found in June and September 2021, the photos taken on the day they were found on the beach:

Found June 2021.

Found June 2021.

Found September 2021.

Note: A good description of the process of wood petrification can be found in Jocelyn Thornton’s “Gemstones” booklet – see page 21 of the online version.

Stone of the Day #7 is here. The Index to the January 2022 Stone of the Day Series is here.