04-30. Dolomite #1.
A strange flower coming down from the Italian Alps? Not quite – the mineral dolomite is named after Frenchman and mineralogist Deodat de Dolomieu in the mid-1700s.
Dolomite is the mineral for week #18 of the 52-week tour of the geometry of Nature. It is usually found in clusters of small rhombohedral crystals – small parallelepiped where all edges are the same length – and has a somewhat “saddle”-like shape. Its color varies from white to tan to pink. It’s part of the trigonal system family.
Dolomite is not often encountered as a gem. It is generally known as an inclusion in emerald, garnet, quartz, and ruby. A fascinating article by Luo, Yang and Shen describes its possible association with nephrite and how it was used in ancient Chinese culture. A major source of magnesium, it is found today in pharmaceutical applications and agricultural products.
From a resource by Steinfink & Sans: refinement of the crystal structure of dolomite.
04-29. Garnet #7.
Crystal-field spectra of a garnet structure from a resource by Ross, Keppler, Canil and O’Neill
04-28. Garnet #6.
The garnet structure is so well balanced and symmetrical, its geometry does make for traditional stain glass window template!
From a resource by Ross, Keppler, Canil and O’Neill.
04-27. Garnet #5.
From a resource by Ross, Keppler, Canil & O’Neill.
04-26. Garnet #4.
Structure of a garnet, front view. From a resource by Ross, Keppler, Canil and O’Neill
04-25. Garnet #3.
What more to say!
The structure of this garnet crystal is so awesome, I just highlighted a few spots here and there.
Now, the most surprising for me is that antic and medieval jewelry takes so much after the geometry of the crystal, I wonder how they did it, not having any of the sophisticated instruments we have today to study nano-size objects.
There are 365 atoms, 642 bonds, 107 polyhedra in this image – not counting the few gems I inserted on the original geometry.
From a resource by Griffen, Hatch, Phillips and Kulaksiz.
04-24. Garnet #2.
From a resource by Fujino, Momoi, Sawamoto & Kumazawa