Minerals : Definition
Minerals are all around us in the natural world and are essential factors in making good quality modern-day life possible. However, we generally live without noticing the existence of minerals though more than 4,000 species of minerals are known to exist. Some minerals like magnetite, cuprite, cassiterite or molybdenite provide essential metals for industry. Many necessities of our everyday lives could not be acquired without quartz, feldspar, mica, calcite or clay minerals. Some minerals with good crystals or colors can be targets for individual collectors or museums. Without minerals, modern civilization could not exist; today we live in houses, work with tools, use cosmetics or decorate ourselves with gems, most of which are made from minerals. Thus, it is no exaggeration to say that our lives are based on minerals.
A mineral is generally defined as 'an inorganically formed and naturally occurring homogeneous solid with a definite chemical composition and an ordered crystal structure'. Quartz, feldspar and mica commonly seen in mountains and riversides are representative examples of minerals. Except organically formed and man-made materials, most solid materials found in the earth surface are composed of minerals.
Animals or plants are not minerals. Pearl, used as a gem, is not a mineral because it is organically formed in a pearl oyster. Man-made gems such as synthetic ruby or synthetic diamond are not minerals, while natural ones are minerals. Naturally formed ice, native mercury and amorphous opal are included in the realm of mineral, while petroleum and coal are excluded even though they are often referred to as mineral fuels.
RhodochrositeArgentina
Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. It shows typically rose-red color, but impure specimens can be shades of pink to brown. It is characterized by rhombohedral cleavage, vitreous luster and a white streak. It is transparent to translucent. It is often confused with the manganese silicate, rhodonite, but is distinctly softer.
Rhodochrosite is infusible, but effervesces in hot hydrochloric acid. When heated on charcoal, it turns black but remains nonmagnetic. It is a minor ore mineral of manganese and is sometimes used for ornaments.
Smoky Quartz & OrthoclaseMungyeong, Korea
Quartz and feldspar are common minerals that are easily observed in nature. The color of smoky quartz results from defects in crystal structure.
OpalPohang, Korea
Opal, regardless of its amorphous character, falls in the realm of mineral.