2 The values of geologic time referred to, based on radioactive methods, especially the age of pleochroic haloes, I propose to criticize on a future occasion. There are good grounds, which cannot ...

Its pleochroic colors differ with its bodycolor. Iolites that appear violet display light violet, dark violet, and yellow-brown pleochroic colors. Bluish iolites display colorless to yellow, blue-gray ...

When you think of expensive gemstones, what comes to mind? Most people think of the Big Four: diamonds, emeralds, rubies and sapphires. However, it might surprise you to know that there are ...