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
Mineral del Monte Mineral del Monte Mineral del Monte, commonly called Real del Monte ( or El Real, is a small mining town, and one of the 84 municipalities of Hidalgo, in the State of Hidalgo in east-central Mexico. It is located at an altitude of . As of 2005, the municipality had a total population of 11,944. The Mine District of Pachuca—Real del Monte has a long and rich heritage. The mines in the district are conservatively estimated to have produced 1.2 billion Troy ounces of silver and 6.2 million ounces of gold. That is 6% of the silver mined throughout the