Here is my finished product.
Here is my inspiration pic. I chose this raw chunk of ruby gemstone so I could get the colors right.
You will need transparent and opaque glycerin melt and pour soap, essential oils for fragrance, a small container of mica colorant (this makes the sparkle in the rock), a spray container of rubbing alcohol, sharp knife and special coloring for soap (NOT food coloring). You can find all of these items at a craft store such as Michael's or a large JoAnn's Fabrics. You will also need a microwave-safe glass container (or two, or three) to melt your soap, a microwave, something to stir with (popsicle sticks do just fine) and several misc. containers to create your crystals. These are the containers of MP soap I purchased. It's by "Life of the Party" and retails for about $5/lb.
I first melted about a cup of the glycerin in the microwave in a glass measuring cup (don't make it so hot your finger can't be dipped into it). Add a drop of coloring until you have the desired shade, a few drops of fragrance and stir with your popsicle stick. I used grapefruit scented oil for my delicious ruby soap. You will notice tiny bubbles formed on the top of your melted glycerin. Give it a spritz with the rubbing alcohol and they will disappear. Pour into separate containers by color and spritz the bubbles on top with alcohol again to get rid of any bubbles. Let set for about 20 minutes until it's cool and hardened.
Gently pop them out of the mold and cut into shapes as desired. This first layer is for the opaque crystals on the bottom of my rough gemstone.
Melt a portion of clear glycerin (don't forget to add fragrance so each layer smells nice!) and pour into the bottom of your container/soap mold. I used about 1/4". Spritz with alcohol to remove bubbles. The alcohol also helps the next layer of your project "stick" to the previous layer.
Add your opaque glycerin bits BEFORE the clear layer hardens. Add a small amount of translucent glycerin on top of that and give it a spritz. This will hold that layer in place.
Here's where the magic begins to happen. Once it has "set" or hardenend after a few minutes, I lightly brush that first layer of opaque crystals with mica using an eyeshadow brush. Get into all of the little crevices and don't be afraid to blob it in some spots. This is what makes the veins in your layer, that wonderful layer of sparkles you can see through the soap.
Spritz it again with the alcohol and then begin your next layer. I used a pale pink color for my next layer. First pour the translucent, then sprinkle the "crystals" you chopped. Spritz with alcohol, add a little more translucent to make it stay in place. Let it set.
Now you can really see the layers start to form.
Begin slicing your larger crystals that will stick out of the top of your soap. For this I used clear, light pink translucent and dark pink translucent. I cut them this way and that to resemble real crystal formations.
Pour some translucent clear and stick them in this way and that. You have to work quickly as they fall over. I just lean them next to each other and cram them in there however they'll fit. Then pour in more soap melt - I used an opaque pale pink for the top layer.
Here's what it looks like once it's totally hardened enough to pop out of the container. Make sure it is totally hardened, or else the center will ooze when you cut into it. I let it sit for at least an hour. Here it is next to my inspiration picture. Not exactly like it but it's MY interpretation of it. Yours will look totally different, too!
But wait a minute. We're not done yet! We have to ice the cake now. Nature doesn't give these gems to us perfectly sliced. So I made some imperfections in the cuts.
Fill in any cuts with your mica powder. I also brush a bit up and down the crystals.
One final spritz of rubbing alcohol to disguise any fingerprints and give it a shiny, finished look and we're done!