Chalcedony to as prase. However, the term prase is also used to describe green quartz, and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.) Blue-colored chalcedony is sometimes referred to as "blue chrysoprase" if the color is sufficiently rich, though it derives its color from the presence of copper and is largely unrelated to nickel-bearing chrysoprase. Heliotrope is a green variety of chalcedony, containing red inclusions of iron oxide that resemble drops of blood, giving heliotrope its alternative name of bloodstone. In a similar variety, the spots are yellow instead, known as plasma. Moss agate
Non-metallic inclusions later stage. Usually nitrides are present in special steels that contain an element with a high affinity to nitrogen. By mineralogical content, oxygen inclusions divide into the following main groups: Ferrites, chromites and aluminates are in this group. By stability, non-metallic inclusions are either stable or unstable. Unstable inclusions are those that dissolve in dilute acids (less than 10%concentration). Unstable inclusions are iron and manganese sulfides and also some free oxides. Present-day levels of steel production allow to move off from the metal different inclusions. However in general the content of inclusions in different steels varies within wide limits and