Ideally your rough will have, blocky cubic dimensions, but you will rarely be that lucky. The reality is you may loose up to 50%, maybe more of the selected rough. Not that the material that is removed is a loss, because it can, if you choose be slabbed for cabochons, or at least worst case, be salvaged for tumbling material. Pay special attention to all surface features that you may want to incorporate or eliminate from the finished sphere. There are many variables that can dictate the ultimate dimensions and quantity.

The next step is to measure the width and the height, of the narrowest side, to establish a rough idea of the maximum diameter the rock will yield. The first stage is to cut a perfact cube. So the first cut is the most critical and needs to be as close to perfect as possible. Because the remaining five sides will have a reference from this cut. Looking at the narrowest end view in the photo above, you will see the left side is convex while the right side is concave. The cut across the terminal face of the horizontal axis will be at the bottom of the concave.

Third step is to take a measure of the length, this will give the approximate number of spheres this rock will yield. The first stage is to cut a perfact cube. From the top photo, it looks like the maximum width will be about 3¼ inches. So with a 5¾ inch measurment along this side, you should get one 3¼ inch cube and a second cube that works out to be about 2½ inches.

Looking at the rock in your hand it is certainly easier to visualize a three dimensional cube extending out and into the rock, as opposed to looking at a two dimentional photo. In a photo you will not see the undulating features of the rock that are not in the photo. Even viewing in three dimensional real life it is difficult at times. Only time and experience will make you good at picking rough.

Keep in mind, the more proficient you become at picking your own rough, the more likely you will know a little more exacting, what the end results will be. The advantage to you is being able to communicate with the cutter what you want or expect. If your estamates are close, then an experienced cutter should be able to see the same thing, and if not explain the flaw in the thought process. In the long run this will make you better at what you are doing, and with what you want your collection to look like.

I am in the process of putting together a better selection of photos to add more value to this tutorial. In the mean time if you have questions or need advise, I am more than happy to communicate my thoughts with you.