Is your find a cube (Pyrite), a prism (Quartz), or a dendrite (Manganese)? The PDF’s photographic index is superior here. Because you are in digital format, you can open the preview thumbnail grid and visually scan 50 images at once until you find a match.
This feldspar displays a flash of blue, green, or gold called labradorescence . Use the PDF’s search term "iridescence" to find this entry. It is hot right now because of the crystal healing trend. pocket genius rocks and mineralspdf hot
Rocks changed by intense heat or pressure (e.g., marble, slate). Is your find a cube (Pyrite), a prism
Here is the PDF version of the file. (Please copy the content and create your pdf using a pdf maker) Is your find a cube (Pyrite)