Cumengite crystals - epitaxial over boleite

Based on a specimen from Amelia Mine, Boleo Dist., Baja California Sur, Mexico

This is one of the iconic shapes in mineralogy - highly symmetrical epitaxial overgrowths of cumengite over boleite. Although my specimen is tiny, its form is good, and finding it was all the encouragement I needed to get started on a model. This was the first model I attempted with nonconvex regions, and I was surprised by how well it worked out. Gluing these models together accurately is difficult, and sanding inside the concave areas is worse yet. But some of the most interesting crystals out there have concave areas, so developing a technique to represent them was clearly necessary!

If you’d like to see more specimens with concave areas, my model of bixbyite with braunite lamellae is a favorite. This iron cross twin and this odd garnet model are also quite appealing. Additionally, most of the models tagged “Epitaxy & Parallel Growth” and “Twin” will also display concave geometry, so they are good categories to check.

Model details: 11" across points. Tetragonal dipyramids are wormy maple, tetragonal prisms are cherry, and pinacoids are padauk.

Specimen details: Cumengite crystals epitaxial over boleite. Amelia Mine, Boleo Dist., Baja California Sur, Mexico. 5mm across.

• Cumengite
• Epitaxy & Parallel Growth
• Tetragonal
• Boleite