Plastic deformation in natural diamonds: Rose channels associated to mechanical twinning

Abstract

Hollow channels in diamond are well acknowledged to be the result of dissolution processes.In this article we demonstrate that some hollow channels in natural diamonds are the consequence of intense plastic deformation by mechanical twinning. Two mixed-habit diamonds presenting numerous geometrical hollow tubes were studied. X-ray Laue analyses showed the presence of microtwins. At the intersection of microtwins, displacements and cracks are generated, creating the hollow channels observed. The presence of the cracks seems to have released the internal stress, as there was less to no signs of deformation at and around them. Further dissolutions are sometimes but not always seen within the cavities. Mechanical twinning, so far mostly identified in pink to purple diamonds, might be more widespread than originally thought in natural diamonds. Graphical AbstractMacroscopic voids (≥ 100 µm in diameter, and sometimes ≥ 1 mm long) are observed in some mixed-habit growth natural diamonds. The voids are created at the intersection of two twins and are interpreted as Rose channels. This figure shows cross sections of the Rose channels by scanning electron microscope imaging and their interpretation.

Natural-Color Pink, Purple, Red, and Brown Diamonds: Band of Many Colors

“…Diamonds are etched by fluids during their mantle residency or during kimberlite ascent (Fedortchouk et al, 2005;Fedortchouk and Zhang, 2011), and these fluids first exploit preexisting weaknesses in a diamond. Hollow channels known as Rose channels can also occur along intersecting twin lamellae (Schoor et al, 2016;figure 18, right). First described by Gustav Rose in 1868, these are formed by the intersection of twin lamellae, where the twinning action can result in a straight, hollow channel with a prismatic opening (Rose, 1868).…”

Microwave Spectroscopy as a Potential Tool for Color Grading Diamonds

“…The nitrogen atom is smaller, at ~56 pm, compared to the carbon atoms, 67 pm [14]; thus, it can contaminate the diamond crystal when carbon atoms are replaced. A brown color occurs (~1-3%) due to plastic deformation: slight deviations from an ideal structure can exist in the crystal as a result of the carbon atoms' position [15,16]. In addition, rarely, boron (B) atoms (which are small compared to carbon atoms) may replace carbon in the diamond, producing a bluish-gray color (e.g., the well-known Hope diamond [4,7,17,18]).…”