Gems and Minerals
To know more about gem and minerals we have t distinguish these two notions and to reveal all the features they have in common. What is a mineral? There are several definitions of this word, so I will let you choose from all of them. First one is – a mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes. That was said in 1995 by geologist Nickel. Before him in 1990 someone called O’Donoghue noted that minerals are naturally-occurring inorganic substances with a definite and predictable chemical composition and physical properties. In the early 60ies there were formed few definitions – 1) These… minerals …can be distinguished from one another by individual characteristics that arise directly from the kinds of atoms they contain and the arrangements these atoms make inside them; and 2) A mineral is a naturally occurring homogeneous solid, inorganically formed, with a definite chemical composition and an ordered atomic arrangement.
But the most correct one, I suppose, was formed in 1898 by Brush and Penfield. There was said that every distinct chemical compound occurring in inorganic nature, having a definite molecular structure or system of crystallization and well-defined physical properties, constitutes a mineral species.
Now let’s continue with gems. First of all gems are minerals, sometimes rocks (in the case of lapis lazuli), and petrified materials. All of them when cut or faceted and polished are collectible or can be used in jewelry. Besides mineral gems there are organic ones – amber, that is fossilized tree resin and a form of coal known as jet. Distinguish precious and semiprecious gems, and some of them are too soft or too fragile to be used in jewelry (single-crystal rhodochrosite). But such stones are usually exhibited in museums and are sought by collectors.
As you now may see that minerals include gems in them and gems are a part of minerals mostly. Each gem has an exact chemical composition, physical properties and is made from the same elements that are a part of that gem’s mineral group. However there could be any other elements in addition to the main ones that may affect color and other properties.
As I have noted before – it is obvious that gems have almost the same properties and features as the other elements from the same mineral group. Physical properties that gems and minerals possess are – hardness, streak, luster, density, cleavage and fracture. Besides the physical properties minerals also have optical properties the presence of which attract people in gems. These are – refractive index and color.
It is important to remember that not only gems are made of minerals, but rocks too. And therefore being a mineral is not enough to be considered a gemstone. Not all minerals from crystals are large enough or maybe good enough, or clear enough to be used as gem stones. The great majority of mineral crystals are hard to be seen or have a lot of cracks or ugly inclusions.
