Which term describes a diamond with grain layers that are not on parallel planes, or one with partial twinning?

Which term describes a diamond with grain layers that are not on parallel planes, or one with partial twinning?

• A. Three-point diamond
• B. Two-point diamond
• C. Twisted stone
• D. Transmission

Answer: (C)

A diamond’s internal grain pattern comes from growth lines in the crystal. When those growth layers end up not lying on parallel planes, or when twinning occurs only in part of the crystal, the grain orientation shifts from one region to another, giving the stone a twisted, irregular look. That combination is what the term twisted stone describes—the grain layers are not on parallel planes, and partial twinning is present. The other terms don’t fit because they describe something other than this specific grain behavior. They’re not about how the internal layers align or how twinning shows up in the crystal, so they wouldn’t accurately capture the described texture or appearance.

A diamond’s internal grain pattern comes from growth lines in the crystal. When those growth layers end up not lying on parallel planes, or when twinning occurs only in part of the crystal, the grain orientation shifts from one region to another, giving the stone a twisted, irregular look. That combination is what the term twisted stone describes—the grain layers are not on parallel planes, and partial twinning is present.

The other terms don’t fit because they describe something other than this specific grain behavior. They’re not about how the internal layers align or how twinning shows up in the crystal, so they wouldn’t accurately capture the described texture or appearance.