epidosite/unakite - meh (16 pics)

[timloco]

So I picked up a bunch of epidosite, we have a lot of that here in CO. I tried to tumble it in my rotary tumbler and had issues. It didn't want to get shiny for the most part. I posted pictures of that attempt in this thread here: forum.rocktumblinghobby.com/thread/57361/epidosite-pics

So I kinda gave up on it and put them aside for later consideration. Now that I have a vibrating tumbler - the uv-10 - I figured I'd give it another try. I did pretty much what the sticky thread "instructions for vibrating tumbler" except I added a 1000 grit AO polish in between the 500 and final polish. That seemed to help,I think. It might have just been the vibrating tumbler that made the difference... Some stuff got shiny, some didn't. The stuff with quartz did really nice. The stuff with granite, ok but not as good as the quartz-y stuff. What looked solid showed pits and cracks after tumbling, it seemed impossible to grind them away.

So, I think I just need to pick my rocks a little more carefully, get more with quartz in it, less with cracks in it... I've seen some really good examples of this stuff all nice and shiny here on these boards, so I know it's possible... Anyways, here's the pics.

[jamesp]

I like that stuff. Always called it unakite. Real nice batch.

[carloscinco]

That looks like really challenging material. Looking forward to seeing you dominate it.

[jollyrockhound]

Nice that is some very hard stuff to get a good polish out of for sure, have fun!

[herchenx]

is this from out in Pawnee? I've done OK on epidosite and the unakite-like stuff that abounds but I've also had a lot like this.

I can't tell what will be good or bad before I start tumbling (usually) but after the first round of rough I usually can see what won't work and toss it into the yard gravel.

[Jugglerguy]

I tumble more unakite from Lake Superior than any other rock. It almost always comes out good. I've found that the stuff that looks like granite tumbles like granite. It undercuts. I try to avoid the speckled stuff that looks like granite now. The streaky stuff does the best. The third and fourth pictures from the bottom look like rocks that would do well for me.

Are you getting them perfect in your rotary tumbler before they go in the vibe? Mine have no holes or cracks before they go to the vibe. In my Lot-O I go 2-3 days with 220 SC, then 2-3 days with 500 AO, 2-3 days with 1000 AO, then about 3 days in polish from the Rock Shed. I use either Dreft soap or Borax in every Lot-O stage.

[timloco]

Yea, this is from the Pawnee mostly.

So, with these there's very rarely any perfect rocks with no cracks. I let some go with some hairline cracks but I did do a borax burnish after the 500 and after the 1000 to try and make sure they were as clean as possible... The vibe really seems to open up any crack or weak spot in this stuff compared to the rotary.

Jugglerguy - do you put the dreft/borax in with the tumbling grit, or are you talking afterwords in between the stages, to clean it out?

I think I just need to be little more discriminatory with this when I pick it up, and what goes to the next stages. I was kinda just going my the color of the rock.

[Jugglerguy]

My rock is from the Lake Superior, so it's already very rounded when I get it. I wonder if the beating it takes from the wave action cracks the weak stuff and leaves the tough stuff behind? My rock rarely has any bad fractures in it. The only problems that show up in the vibe is the undercutting of the softer stuff in the granite.

Lately I've been putting a tablespoon of borax in my 4.5 pound Lot-O barrel before I put in the grit. I let it run for a couple minutes and then add the grit. I also do a good wash with borax or Dreft between 1000 grit and polish. I used to let it run for 4-5 hours, but now I'm running it a couple hours, rinsing it, then running it again for a couple hours. It might be overkill, but the water is pretty dirty after the first wash and cleaner after the second. I also switch to a different barrel for polishing. I've been doing a shorter wash between all grits lately, although I got good polish on this stuff in the past without doing thorough washes between each stage.

Here's a picture of my latest batch:

[timloco]

Yup, that's the picture I was thinking about as an example of what this stuff could look like. Outstanding shine. I just need to go back out onto the prairie and collect some more. Oh, darn :-)

[pghram]

I think there's still potential in them. I would take them back to coarse in a rotary to remove all of the pits & cracks. The ones with a lot of mica may underct, but I wouldn't give up on them just yet.

Rich