A cluster of interlocking pyrite crystals with flat reflective faces and sharp edges.
The thing people notice first is that it looks manufactured. Faces meet at clean angles, edges run straight, and the surfaces are flat enough to throw a reflection. Nothing cut it. Pyrite's atoms stack in a cubic arrangement, and when a crystal has room to grow undisturbed the external shape simply reports that internal geometry outward.
The same mineral can finish as a cube, as a twelve-sided pyritohedron, or as an octahedron, depending on the conditions it grew in, and a single cluster often carries more than one. Look closely at the flat faces and you will usually find fine parallel lines across them. Those striations run in different directions on adjoining faces, and they are one of the quickest ways to tell pyrite apart from gold, which has no crystal faces like this and no striations at all.
Mineral: Pyrite (iron sulfide, FeS₂)
Crystal system: Cubic
Origin: Peru
Hardness: 6 to 6.5 on the Mohs scale; hard, but brittle, and crystal edges chip rather than scratch
Treatment: None
Dimensions: 9.5 x 6.9 x 8.9 cm
Weight: 425 g Note: Keep it somewhere dry. Pyrite reacts slowly with oxygen and moisture, and the reaction produces sulphuric acid, which is what damages a neglected specimen over time. Do not seal or varnish it. That traps moisture in rather than keeping it out, and makes the problem worse.
You will receive the exact piece photographed.