>Athavale noted that even if the crystallization process happened in 100 primordial lakes, Earth’s magnetic field would ensure that they all produced precursors

>Athavale noted that even if the crystallization process happened in 100 primordial lakes, Earth’s magnetic field would ensure that they all produced precursors with the same handedness rather than a mixture. I don't get it... Every grain of sand has two sides, so why wouldn't the crystals be equally likely to form on a north pole as a south pole?