The fundamental reason why non-magnetic diamonds have higher strength than magnetic ones lies in the destruction of crystal growth and structure by magnetic impurities (inclusions).

Pure diamond crystals inherently lack magnetism. The reason synthetic diamonds exhibit magnetism is primarily because, during the high-temperature and high-pressure synthesis process, residual ferromagnetic and paramagnetic substances from the catalyst (such as Fe, Co, Ni) form inclusions within the crystal. These residual impurities directly affect the crystallization quality of the diamond, which is specifically manifested as follows:

Non-magnetic diamonds have higher crystallization quality: Microscopic observation reveals that non-magnetic diamonds, which are free from the interference of magnetic impurities, exhibit full crystal growth, very smooth crystal faces, and a higher proportion of complete crystal shapes. At the same time, they contain very few internal black spots and inclusions, and have good transparency. This intact and dense physical structure allows them to withstand larger breaking loads.

Magnetic diamonds have numerous structural defects: Diamonds with magnetic impurities often have incomplete crystal growth and more surface defects. In addition, the crystals contain more black spots and inclusions, resulting in poor transparency. These surface etching pits, cracks, and internal impurities easily become weak points for stress concentration when subjected to force, thereby seriously damaging the compressive strength of the diamond.

In short, the increase in internal inclusions and surface crystal defects caused by magnetic impurities is the core reason why magnetic diamonds become brittle and weak. In contrast, non-magnetic diamonds, with their more perfect smooth crystal faces and higher internal purity, exhibit a measured strength that is about twice as high.