July tumbler yield

kw: observations, photographs, gemstones

Over the weekend I unloaded the tumbler from the last run, which took five weeks. When I bought this tumbler, a Thumler Model T-100, it came with just over a pound of mixed agates and similar stones. Most were of rather ordinary quality, grab bag stuff. I added a pound of jasper from Lavic and a few pieces that a friend gave me, which did come from a grab bag he got at a rock show (I gave them back, polished) . The images below are close-ups showing about one square cm of two of the polished stones.

Lavic Jasper is a moss jasper, or filamentous jasper. The best specimens have these little blue "stars", tiny fortification agates, that fill vugs in the original rock. They represent a later stage of development, an agate filling of an initially soft, filamentous material.

The scattered white spots indicate that the polishing is not complete. I'll get out a leather lap and hand finish the piece.

It has now been about a year since I last collected at Lavic, as I reported last March. I have one piece that weighs more than a pound, consisting if this fine red-and-blue jasper. I am loath to break it up for tumbling. It is nearly spherical, so I may hand grind and polish it into a roughly spherical "quasi-tumbled" piece. That'll have to wait a while, until I have time to join a rock club that has equipment I can use. I don't really want to buy a Genie or similar setup for one project.

This piece is moss agate, the best piece of the ones that came with the tumbler. It is more multi-hued than most moss agate, and more finely filamentous also. Classic moss agate consists of mossy green filaments in milky chalcedony, so that it looks like a plant trapped in the rock. The green color is from reduced iron, just as red is from more oxidized iron. In the piece shown here, there is more than one coloring mineral present.

Sad to say, in both these cases, the areas pictured are the best area in a stone that is overall much less attractive. While I could cut them down, the resulting gems would be rather small. Jasper and agate look best when at least 2cm across. It is hard to see the charm in polished bits the size of a little fingernail.

The next tumbler load will be all jasper again. I'll wait to start until after vacation season; I don't like to interrupt a tumbler run, which needs 4-6 weeks of daily care.