Saturday, June 23, 2012

Rough Rock

Because I have my own lapidary equipment, I can save a lot of money by buying rough rock, and cutting/polishing it myself. I use my own cut gems in my own metalsmithing work, as well as sell them online in my etsy shop. Today I thought I'd show you some of my rough rock and how I purchase it. Usually I buy it online, because the choices far exceed the amount of choices I have at my local lapidary club show. For example, the smooth rock below is a 6" stone from Washington State:

This is actually Washington State Jade. It has a lovely blue-green color with dark inclusions. It comes in these large roundish forms and then I am able to saw off slices of it using my 10" slab saw. This type of stone is easy to mine and produces very little waste- I can get many, many cabochons out of this one rock, so it's worth my time to cut it down into slabs. Once it's in slab form, it's easier to mark and cut into shapes for stone-cutting- but I'll show you that in another post.

Some stones are not available in as nice a package as the jade. Some, as the chalcedony above, form in the earth in a much more disorganized way, making the mining of them a bit harder, and making the rough a bit harder to use. These pieces of rough could probably be cut down into a piece or 2 each, but there will probably be some pieces that are nicer than others due to the variety within the stone. There tends to be more waste in this type of rough. These do tend to make good carved pieces, though, because of their irregular shapes, as well as nuggets or beads. Sometimes I might look at a piece for a long time before I decide how I'm going to cut it!

Above is rough Ethiopian opal. It, too, comes in an irregular shape, and they can be challenging to cut 'right'- meaning it may take a lot of looking before deciding which orientation to cut them.

Some stones don't look like much on the outside, but once you slice them open.....

they reveal a gorgeous interior! This is a nodule of Laguna agate.

One of the easiest ways to buy rough stone is to buy rock already slabbed. It may cost a bit more per slab, but much of the work is already done. Above is an example of Imperial Jasper. I bought each slab separately. One thing the online dealers do to help you shop is they will show you a picture of the slab dry, as well as wet. The reason for this is the wet slab will best approximate the look and colors of the stone when polished. When I was shopping for rough rocks at the Tucson gem shows last year, all the vendors had water available in spray bottles for this exact purpose. For example, the above stone is dry, but the stone below is wet.

You can see from the above picture that the stone slabs portray a lot richer colors when wet, which is what you will expect when the stone is cut and polished.

The above slabs are some of the ones I cut from a 'tube' of Wonderstone. You can start to see the alternating bands of mustard, burgundy and rose, but look at the below pic of the slabs wet:

Once wet, the slabs' colors are much more saturated, which is what they look like once cut and polished. 

Above is a rough rock of Morgan Hill Poppy Jasper that I've been cutting into slabs. The above pic shows the face dry, and the below pic.....

... shows the face wet- much more saturated colors. Rough dry rocks tend to look hazy or frosted so that's why it's necesary to wet them in order to approximate the look/color of the finished stones.

One more example- the above stone is a piece of Koroit opal from Australia, pictured dry.

And here is the same piece, pictured wet.

Another important factor of cutting down a slab (other than aesthetics) is the appearance of fractures within the slab. However you want to call it- cracks, crazing, etc... these areas of the slabs are a bit problematic to work with. Many types of rocks have fractures- sometimes they're actually healed, which means they've been filled in over time with more rock and are quite stable. But other times they bely a weakness within the stone. I try to avoid having a fracture appear in my finished stones, and therefore I tend to cut the affected slabs, such as the Montana agate above, along the fracture lines, and then use the areas within to form cabochons.

However, some stones are so fraught with fractures! Morgan Hill Poppy Jasper is one such rock. It's often times impossible to avoid all of the fracture lines, and in doing, you get very small cabs with very little patterning. In this case, whenever I get a piece of rough that I know is known for fractures, I follow the advice of a lapidary friend: I hold the rough rock from 2 feet above the concrete floor, and drop it. Whatever fractures aren't stable, will break apart during this time. Then, whatever is left I use knowing it may look all cracked up, but it's actually quite stable. Just remember- every crack is not the kiss of death. Many stones have them, and they will not become worse over time or detract from the beauty of the stone or even affect the wearability or strength- they were part of the forming process of the stone. In stones such as the poppy jasper above, I like to think of the crazing as part of the character of the stone!

If you find a crack in a stone, have an experienced lapidary look at the stone to determine if the stone is stable or not.


  1. Thank you so much for this fascinating and informative blog on how you go about cutting your stones. Your photographs really illuminate the process.

  2. Thanks so much for checking out my blog!! :) Dana