gemsociety.org

EgPed TIL that the reason crystals and rocks feel cold to the touch is that they have "high thermal inertia". In other words, a rock that sits on a table in a 24°C room will want to take in heat from our 36.8°C bodies,.. and that feels cold. Once it has gained that 12.8°C it does not feel cold any more.
OovwY TIL Weddellite crystals can be found at the bottom of a sea near Antarctica and in kidney stones in the human body.
QJPve TIL That diamonds are the most common gemstone in the world and that most of them are mined by a corporation known to have used murder and kidnapping in order to corner the market.