While crystals and gemstones are often admired for ... Historically used as a pigment, realgar was later found to be dangerous due to its arsenic content. Prolonged exposure can lead to arsenic ...

The miners had found what would soon be known as the Cave of Crystals, a natural wonder that would capture the world’s ...

Minerals are typically formed when molten ... Diamonds, made of carbon atoms, are the hardest natural substance found on Earth. Formed under extremely high pressure hundreds of miles underground ...

In other words, a transparent crystal cannot be regarded as optically ... the present writer that the effect to be expected may be found in the following way:—If the principles of statistical ...