Khan academy is a great site to learn about all types of courses, including science. Their science courses cover just about everything that needs to be known, such as chemistry. Many people use their courses to help understand what they learn in school, or just to learn! All the courses make learning fun and easy.
This site contains a large list of in depth descriptions of Gemstones. Gemology is a very interesting science that anyone can study! Above is one on my favorite gems, the Citrine, a quartz gem that represents light and energy.