u/loonattica

This is a mix three different sizes from Gem Center USA: .5-1” / 1-1.5” / 1.5-2”

I tried an extreme regime of stages, without a crazy improvement. Results are fine, but not EXTRA FINE, and that’s what I was hoping for.

Rotary QT-66:

1. 180 SC, 8 days
2. 400 SC, 7 days

Vibe- 2 barrels of MT-10, intermingled at each stage grit change:

3. 800 SC, 2 days
4. 1500 AO, 2 days
5. 2500 AO, 2 days
6. 8000 AO, 2 days
7. 22K MA, 3 days
8. 60K Raybrite A, 2 days
9. Cerium Oxide, Standard Grade 2 days

Step 8 was a surprise. My first time using Raybrite A from Kingsley North, .5 Micron approx 60,000 grit. It was a downgrade from the 22,000 Micro Alumina. I was expecting little black mirrors, but the surface had a very fine haze. I thought I might have contaminated the mix, but this was spread across two different barrels. I returned to what worked on previous batches: standard grade (not optical) Cerium Oxide. I believe that polish is about 3 micron, more “coarse” than the 22,000 Micro Alumina, but it seems to produce a better polish on obsidian. My understanding is that CO generates a chemical reaction producing heat that results in a finer polish.

Larger size from Gem Center USA.

QT12 rotary:

1. 46/70 SC grit, 7 days
2. 330 SC, 5 days

UV-18 vibe:

3. 600 SC, 2 days
4. 1200 SC, 1 day
5. 8000 AO, 3 days
6. 22k MA, 2 days

I was a little disappointed in the final results. They still look better wet. Fine polish stages were still removing enough material to turn the slurry red. Need to experiment more with this before it’s right. The stones feel really nice. Coarse grind in the 12 pound rotary was a cacophonous surprise. Clunkety clankerson, 24/7.

MCL from The Rock Shed.

3-4 weeks coarse/medium grind in rotaries (QT-66) followed by four pre-polish and polish stages to 22K MA in UV-18 vibe.

Recently tumbled stock from The Rock Shed.

The Rock Shed stock.

QT-12 Rotary:

1. 36 grit + Old Miser = 8 days
2. 46/70 grit + Old Miser = 6 days
3. 180 grit + Old Miser = 6 days
4. 320 grit + Borax = 6 days

Thumler’s UV-18 Vibe:

5. 320 grit + Borax & Dawn, 2 days
6. 600 grit + Borax & Dawn, 2 days
7. 1,200 grit (SC) + Borax & Dawn, 3 days
8. 8000 grit (AO) + Borax & Dawn, 2 days
9. 22,000 (MA) + Borax & Dawn, 2 days

April 14 to May 20, 2026

My first experience with obsidian went rather well. Kingsley North stock.

3lb Harbor Freight tumbler:

1. 180 grit + Borax, 6 days
2. 400 grit + Borax, 6 days

4lb MT-4 Vibe:

3. 800 grit + Borax & Dawn, 2 days
4. 1500 grit AO+ Borax & Dawn, 2 days
5. 8000 grit + Borax & Dawn, 2 days
6. 22k MA + Borax & Dawn, 2 days

Always thought this was just another live oak until I got up close, saw the tiny flowers and dozens of busy bees…

Material from Kingsley North- source location unknown.

Tumbled in small 3lb rotaries for shaping. Moved to Diamond Pacific MT4 for final polish to 22K MA.

I’ve been excited to finish this batch. Nice large stones with extra exceptional chatoyance and beautiful hematite veins.

Started May 11, finished June 7. Eight-stage tumble, 27 days total.

Lortone QT12:

1. 46/70 grit, 7 days
2. 80 grit, 8 days
   (Old Miser added, both stages)

Moved to Thumler’s UV-18:

3. 180 grit, 2 days
4. 400 grit, 2 days
5. 800 grit, 2 days
6. 1500 AO grit, 2 days
7. 8000 AO grit, 2 days
8. 22,000 MA, 2 days
   (Borax & Dawn added all stages)

Final result approved by 15 year old Biskit the Cat.

9:15am Friday morning, I-10, Avalon Coach with 3 motorcycles, additional lead escort and rear sheriff truck, weaving across three lanes of traffic to prevent anyone from passing the bus.

I think this was about 3 or 4 pounds of crushed Amethyst from the Rock Shed. It was a one-off lot, with less fractures than common stock. Mostly clear, with a some orange tints here and there.

Started in the Harbor Freight rotary then moved to MT-4 Mini Sonic for polish. Final polish was 22,000 MA.

This batch started by cutting fractured faces on Harbor Freight tile saw, grinding them smooth(ish) on the edge of the blade, then tumbling in Thumler UV-18 vibratory tumbler:

120/220 grit - 36 hours
400 grit - 36 hours
800 grit - 2 days
1500 grit - 2 days
8000 grit - 2 days
22000 MA - 2 days

There are still minor cracks and fractures, but I like the resulting rounded facets. That UV-18 is FAST!!

I’ll post a before pic in the comments.