Tumble finish your Crater finds!

By Waymon Cox

 Greetings from Crater of Diamonds State Park! While talking to a few visitors after a recent diamond mining demonstration, a man asked me what other rocks and minerals could be found at the park. He said that he wasn’t here necessarily to find diamonds but to collect other rocks and minerals that could be polished or cut. While some people come here with their hearts set on finding a diamond, many visitors understand that other rocks and minerals found here can also have value, depending on what is done with them.

 Rock tumbling, or tumble finishing, is a process used to beautify many Crater rocks and minerals to enhance their personal or monetary value.

 The most common tool used in tumble finishing is the rotary rock tumbler, a machine which uses a rotating rubber or plastic barrel and abrasive grit to turn rough rocks and minerals into beautiful, polished specimens.

 The rock tumbler emulates natural forces, such as ocean waves or river rapids, which grind and shape rocks and minerals over a very long time. Two to three abrasive grits, as well as a polishing compound, are added to tumbler over several weeks to smooth and shine the stones much faster than nature. Water is also used in the barrel as a lubricant, allowing the stones to move easier and helping prevent heat buildup during the process.

 Beginning with coarse grit, the stones are tumbled 24 hours a day and inspected on occasion to check their progress. Each week the stones and barrel are thoroughly cleaned (outdoors, to keep household pipes from clogging with used grit), and the stones are returned to the barrel with finer grit to continue removing rough surfaces. During the third or fourth week, an ultrafine pre-polish is typically used to make the stones’ surfaces as even as possible.

 Lastly the pre-polish grit is replaced by a polishing compound to give the stones a beautiful shine. This final step usually takes seven to ten days before the stones are completely polished.

 Popular “polish-able” rocks and minerals found at the Crater include jasper, agate, quartz, and conglomerate. Most of these can easily be found in the park’s diamond search area and come in an assortment of shapes and sizes that are perfect for tumbling. Rock tumblers are fairly inexpensive to own, meaning that almost anyone can enjoy this fun hobby!

 Right now I am tumbling a batch of stones to give to kids and use in programs during the summer. As I clean and check the stones each week, I am always eager to see how they are progressing. The entire process of tumble finishing can last a month or more from start to finish, but the beautiful results are well worth the wait!

Search area last plowed: March 6, 2013

Most recent significant precipitation:  March 23, 2013

Diamond finds for the week of March 17, 2013 (100 points = one carat):

March 17 - Adam Hardin, Barberton, OH, 27 pt. yellow

March 19 - James Ummel, Houston, AR, 9 pt. white

March 20 - Ron Cudmore, Berryville, AR, 3 pt. brown; Jim Graham, Prescott, AR, 5 pt. yellow, 12 pt. yellow; Mikhail Hentz, Lamoni, IA, 3 pt. white

March 21 - Peeka Traver, Mountain Home, AR, 3 pt. white