And in my opinion if you are going to spend the money on onyx you may as well put some lights behind it.
Working with onyx alone isn't easy. It's a more difficult stone to work with for many reasons. Throw backlighting into the mix and it makes it even more difficult. Backlighting onyx isn't just throwing whatever light you want behind it. I've seen many backlit onyx pieces look horrible and it's sad because I'm sure the homeowner paid good money for the stone and the fabrication/ installation.
There are a few factors to consider when backlighting onyx...
1) Make sure the onyx is transparent enough. Some onyx slabs just won't show the light well. I use a flashlight to test all areas of the slab before committing to backlight it.
2) Choose the correct lights. I have some secrets of the best lights that I'm not going to share here (sorry, sometimes I just don't feel like helping out my competition). All lighting is not created equal. You want a nice soft, overall glow. You shouldn't be able to SEE the lights, unless it's a design decision that you want to and you have them carefully designed and placed.
One more hint....make sure they are lights that last awhile. You don't want to be going through the hassle of changing them all the time. Also on that note, make sure you have access to change them. Seems like common sense right? Unfortunately I've seen people forget that small step.
3) Work with an experienced and reputable fabricator. You will pay more for this fabricator, but I promise it will be worth it. There are tricks to placing the lighting and installing the slab. There are tricks to choosing the right slab of onyx and fabricating the piece. All of this knowledge costs money. Sorry, but you get what you pay for in the stone industry.
Here's a picture of a poor installation of backlit onyx countertops. I'm not going to credit this photo because I got it from the fabricator's website and...well, I shouldn't embarrass them.
I don't want to end this on an ugly note, so here is another beautiful (and correct) installation...
Have a great weekend!