Enemy or foe is an individual or a group that is seen as forcefully adverse or threatening. The concept of an enemy has been observed to be basic for both individuals and communities.
A diffractometer (pronunciation: di-frak-'tÃ¤-m&-t&r) is a measuring instrument for analyzing the structure of a material from the scattering pattern produced when a beam of radiation or particles (such as X-rays or neutrons) interacts with it. Principle
The tools used by gemologists for the identification and grading of different gemstones range from the simple and familiar to the high-tech and exotic.Most gemstones can be identified by a few basic tools that every gemologist should have at hand.nother required tool for gemologists is the refractometer. A small drop of liquid with a high refractive index (RI) is placed on a glass cylinder in the top of the refractometer and illuminated from a separate light source (sometimes white light, but a monochromatic light source provides better accuracy).