Customer Reviews
Too many steps - too much time 
2007-01-19
It takes at least 16 days to get polished rocks with several steps to e taken at eacer phase. Also, not enough rough rocks in initial package for the $80 dollars paid. Discovery Kids offered it at $30 dollars less on its website. However I did not see the reduced pricing until after my item was shipped from Amazon - on the same day of order. I also did not want to chance not getting it before Christmas.
It Rocks 
2007-01-19
This space-age looking rock polisher really works quite well - not as fast as suggested in the advertising, but the results are great and it is easy to use. Following the recommended cycle times, it takes about 16 days to get a polished rock. If you are using beach rocks, the first stage can be skipped, making it a 10 to 12 day process. This is a bit long to hold the attention of smaller children but my 8 year old is OK with waiting. The unit is a bit noisey and the vibration causes the unit to move around on a flat surface, so it can fall off tables. We just put it in a corner in the basement. Overall I am quite happy with it.
Rock Tumbler 
2007-01-15
It takes about 16 days to complete a cycle, which is normal. However, unit STOPPED working on 14th day. THIS WAS THE FIRST TIME USING IT RIGHT OUT OF THE BOX, NEW. Don't waste your money.
Spins too fast 2007-01-04
I'm having the exact opposite problem as the previous reviewer (who reported the motor sometimes stalled). My tumbler spins too fast. We are a couple days into the first polishing step, and every time we open it up to check progress we find many of the rocks are stuck fast to the mouth end of the tumbler (the barrel tumbles end-over-end) with the polishing compound caked hard around them. I timed the rotation rate at about 2.4 revs/sec, which I figured out (after Googling some physics formulas) is just fast enough that the rocks should stick at the ends instead of tumbling, which is exactly what is happening. I'll update this review and increase the rating if the rocks turn out well despite this, or decrease it even more if it doesn't work.
If you bought one of these, please add your review so we can see if others spin too fast or stall too!
I also was surprised by how loud this machine is. We ended up putting it beside our oil-burning furnace, and it is quite a bit louder than the furnace.
Also, beware that it vibrates a lot and thus moves around due to the high rotation rate. We ended up putting it on the floor after it almost fell off a table in the first hour.
Takes too long. Noisy. Weak Motor. 2006-12-26
Bought this for my 5 year old nephew. We thought it would make a great gift for the holidays. Then we read the instructions. Here are the cons:
1. (Time)
There are 4 stages to polishing and the whole process can take 17 days. Let me emphasize: the machine has to be running almost constantly for 17 days (minimum).
2. (Noise)
The polisher consists of a sealed container mounted on a gyroscope run by a motor. When running, the motor and the assembly are noisy. I would not buy this is if I lived in an apartment. Even in the house, I can hear it from 1 floor away.
3. (Weak motor)
I might be persuaded to recommend this product if not for the weak motor. The machine has a tendency to "stick". The tumbler stops tumbling and you've got to nudge it to get it going again. I started the first stage three days ago and I've had to nudge it 10 times. This can only add time to the process.
Great Gift for my Patient Daughter 2008-01-07
This was her favorite gift at Christmas. She is very patient and has followed the instructions to the min. She is loving it. We did move it out to the garage because she couldn't sleep. It was worth every penny.
Fun and Educational 
2007-08-01
First of all, I feel that the Discovery Gyrotek Rock Polisher is a very well-designed toy. But judging from some negative reviews here, it is obvious that some people have absolutely no idea how rock polisher works before buying this item. That's why they complained about "It takes too long", "Too many steps", and "Too noisy". Here are some background information you need to know:
There are two main types of rock tumbler or polisher: rotational and vibrational. A typical rock tumbler toy uses a slow rotating drum/barrel to polish rocks. It is inexpensive but takes at least 4 weeks for the complete process. A vibrational polisher shakes the barrel vigorously to reduce the polishing process down to about one week, but it also costs a lot more.
This gyro rock polisher is a good compromise between the above two types. As the barrel is being spinned up and down, it also oscillates left and right. So rocks inside are tumbled as well as shaked. Therefore the whole 4-step polishing process is compressed from 4 weeks to 'only' 17 days. The machine does make noise when running, but not intolerably loud. Just keep it in the basement or garage and you'll be fine. If necessary, you can even cover the whole machine with a blanket to absorb its sound and vibration.
Of course, 17 days may still seem too long for kids (and some adults) with short attention span. So those people looking for instant gratuity should just go play video games instead. For the rest of us, however, this rock polisher can be both a fun toy and an eduactional tool.
As with any educational tool, you can get the best result by participating with your kid. Encourage your kid to read up more about rocks and minerals. Stress the importance of patience and ability to follow through a multi-stage experiment. Mark your calendar and keep record for the progress, and so on.
There was one minor problem I noticed about this item. Several times it stopped tumbling within a few hours into a polishing cycle. I concluded that it was due to excessive vibration of the machine, which eventually triggered a safety shutdown. I covered the dome lid with a piece of rug to damp the vibration, and the problem went away.
Easy to use. 2007-03-18
I researched rock tumblers carefully before deciding on this particular one. I am thrilled with how easy it is for my 11 year old to use. The one thing we were not prepared for was the length of time each of the 4 steps takes to complete (up to 7 days for each step). Which means, your tumbler runs, 24 hours a day for nearly 4 weeks. While this one is relatively quiet, especially compared to cheaper versions, be prepared for the drone of the tumbler for extended periods of time. If you youngin' is impatient, this might not be the best choice of hobbies as it is time consuming and there is NOTHING to look at for weeks at a time. On the other hand, this produced some gorgeous polished rocks with little effort.
Best of the cheap tumblers 2007-01-23
I have used a different cheap plastic tumbler, and read about a lot of others, and while this one isn't perfect it is the best of an imperfect lot. My rating is based on equivalent priced items. Comments on a few issues:
- Noise: Yes it makes some noise, but the rubber barrel cuts this down a LOT. All you really hear is motor noise, and some dull sloshing. Much better than the ones with the plastic drums where you hear the rocks RATTLE RATTLE RATTLE-ing 24/7.
- Time: The standard drum-type tumblers take at least 50% longer to produce the same results. Bottom line is if you want to tumble rocks you need to have patience, and this one is faster than most. NOTE: I understand the vibratory ones are faster, but I looked and I didn't see one for under $100.
- Rotation Speed: I felt the same as the earlier comment about the speed when I first started it, that it was too fast. I would stop it a couple times a day and shake everything loose from the ends. I did try playing with the mix a bit, and found it you minimize water to JUST enough to cover the rocks (as the directions do say) it oscillates OK (still not perfect in the early stages). But I was pleasantly surprised after stage 1 that the rocks were actually adequately tumbled. And each subsequent stage they are getting smoother, just as advertised.
- Motor Life: One reviewer said their motor burned out...I am on stage 4 of my first cycle, and have had no problems. The individual may have had a lemon. When I contacted Discovery (via the email in the manual) about my motor speed concerns, they didn't offer any technical advice like I hoped, but they did provide instructions for returning it if I wanted a refund.
- Supplies: Every tumbler out there comes with a few rocks and polishing compounds, but none come with much. They want to hook you in and make you buy more, obviously. This one comes with enough stuff to tumble 2 full sets, then you are on your own. It's enough to see if you are really interested.
Bottom line: Good toy for the price you pay.
Great Fun 2007-01-22
I purchased this rock polisher for my daughter. She and I are having fun while learning about geology. I'm very happy with my purchase. It takes about 17 days to polish the rocks. It does a great job in polishing the stones.
Oppenheim Toy Portfolio, 2005. The Best Toys, Books, Videos, Music & Software for Kids