CopyRight @ 1998
I only put this in here, because I repeatedly see this question asked. Abalone shells are made of Mother Of Pearl and this gives them the beautiful iridescence on the inside. The outside of the shell can be a vivid red or green, but usually needs some cleaning to look real good. An Abalone shell can be cleaned up as a fairly decorative memento of fun diving. Of course, they can also get to be a nuisance.
All of the different type of Abalone have shells are pretty neat looking, if you get a good specimen. White and Black Abalone have a delicate white iridescent Mother of Pearl. Red Abalone have bright green and blue Mother of Pearl and the outside of the shell can polish up a very nice red. The Green and Pink abalone have brilliant blue and green swirls of Mother of Pearl. A really nice specimen of a Green Abalone shell used to be called "jewelry quality"... until the far more spectacular shells from south Pacific abalone showed up. Still the Greens are really beautiful and are the prettiest of the California abalone. Polished up, the outside of Green and Pink abalone, are a deep green.
When the outside is cleaned up as desired, the inside can be treated to bring out the iridescence of the Mother of Pearl. It can be covered in lacquer or a liquid plastic like Varethane, but I prefer to rub on a bit of good oil, like Vitamin E oil. It has to be cleaned occasionally, but, it accentuates the colors best.
Red Abalone may have a really nice shell, but much of the iridescence may be cloudy. With a bit of rubbing with a finger, some of this cloudiness may be removed, to show more iridescence.
Cleaning the outside of the shell is another matter and is the commonest question. There are a number of things you can do to clean them up. The best bet though, is to start with a fairly clean shell in the first place.
First thing is to use your iron to break off all of the big stuff. The barnacles and worms are the hardest. They break off pretty well, but it may be pretty difficult to get off the last bit. A wire brush can be used to get off much of the big stuff from the outside of the shell as well, especially if the shell has been allowed to dry for a time.
Then an acid like muriatic pool acid can be put on the shell to dissolve more of what is left. This tends to take some time, caution and repeated efforts. What I think works far better, is to put the shell under a rain downspout. In a couple of days of rain, almost everything gets cleaned off of the shell. It makes the color quite available and requires no chemmies.
If you have good color on the outside of a shell, it is worth it to put on some Varethane or something else to accent the color.
I have made buttons from abalone shell. I also have made a couple of carvings from it too, but the stuff is incredibly tough and hard to work. Also the dust from it must not be breathed. It will stay in the lungs and cause a type of asbestosis. Only try to work Abalone shell if you know what you are doing.
Abalone shells make an odd, interesting and decorative trophy. They are really pretty and I figure that it makes some people wonder, "who made this weird ashtray". They always bring to mind some fun dive or another.
..... I have kept only 2 Ab shells over time and they are both greens.