Which type of diamond contains boron in the lattice with negligible nitrogen?

• A. Type IIb
• B. Type IIa
• C. Type Ia
• D. Type Ib

Answer: (A)

Diamonds are classified by impurities in the crystal lattice. When boron is present and nitrogen is negligible, the diamond falls into Type IIb. Boron introduces an acceptor level in the lattice and gives the stone a blue color; its nitrogen content is essentially undetectable, which is why the characteristic is described as boron-doped with negligible nitrogen. The other impurity patterns don’t match this combination: Type IIa diamonds are essentially nitrogen-free and boron-free, so they’re typically colorless; Type Ia and Type Ib diamonds contain nitrogen (either in aggregated or isolated form) and thus don’t have the boron-related blue coloration. Therefore, the description best fits Type IIb.