Grading for gemin is alot like the grading for gemstones on Earth in a variety of ways. The same 4 characteristics determine a Gemin's value; Carat, Color, Clarity, and Cut. Some of these things have much less importance to gemin value compared to their earthly precious counterparts. The main reason for this is that gemin are processed for their practical use, and not for their visual appearance.
The Carat (ct) is a unit of mass equal to 0.2 grams. This unit is used across Una as a base unit. Stone (st), another unit of mass, is 5184 Carats equal to 1.0368 kilograms.
The Carat (ct) weight of a gemin is not very important. It determines the maximum capacity of magical force the stone can retain, but not the strength of that magical force. It is the capacity of its battery, but not its voltage. Larger stones are less common than smaller ones, for this reason larger stones tend to be more valuable. Stones are graded by the size of their smallest diameter, a good indicator of their maximum potential power output. Generally, gemin work more efficiently when spherical in shape.
To add to this confusion, Carat is also a measurement of length. A Carat (c) is one quarter of a Set (s), and a Set is approximately 1 inch. Gemin are measured by their diameter in Sets. An ideal stone is about 2-5 Sets in diameter.
Price for gemin is based on its spherical volume, as well as its quality grade. The base unit of currency for this world is an poor grade gemin of 1 carat in diameter. The density of Gemin is about 264.42 carats per cubic set. Diamond is 287.59 carats per cubic set.
Gemin come in a spectrum of colors. In general, they are categorized based on their emission wavelength. Most gemin only radiate one color of light, though many exist that radiate multiple colors; which happens only among off-spring of Keygemin after breeding. Gemin colors are rated in Aspects. Aspects perform different actions, some desired, some not.
Unlike size, color intensity is the greatest indicator of the maximum power output of a gemin. The saturation or vibrancy of the color, and its ability to radiate light is measured in a dark room or specially constructed box with a polarizing filter. It is graded on a couple total criteria that will class the gemin.
Brilliance is a measure of the quantity of visible light emitted over time, similar to the SI lumen. The amount of light is graded on a logarithmic scale. Grade S being approximately as bright as an LED flashlight. Grade A as bright as a well lit white surface. Grade B as bright as the full moon on earth, all the way down from Grades C, D, E, and F. Which have no discernible glow even in total darkness.
Hue is the stone's deviation from an ideal standardized set color used for a particular application. Not all hues emitted from a stone are desirable. A stone with red emission will expel heat energy, where a orange color emission will begin to emit impact force. For example, a gemin used as fuel for an engine is more desirable to be centered on red light emission, or slightly toward magenta in order to prevent engine knocking or kickback. Though, in the opposite direction of emission, towards magenta, gemin can produce volatile gases in exhaust. For this reason the emission spectrum for gemin engines is regulated.
Gradience is a measure of the difference in the emission of light color from different points on the stone. As the emitted color can fluctuate over the stone's surface. A more consistent color will indicate a more regular operation, especially in sensitive devices or mechanical applications where power output needs to remain constant. Gradience can vary wildly between points over the stone, and may even manifest as a gemin with multiple aspects. These stones are rare and highly valuable, either to Gemites or those looking to possess powerful Keygemin companions.
Transparency is the most important indicator of gemin quality. Pure gemin are typically mildly transparent. A completely opaque gemin is almost never of good quality, but a completely transparent gemin indicates that it has consumed most of its available stored energy. An ideal gemin should be continuous in its transparency all the way though. With quality indicated by the material's clarity.
Clarity in gemin is the lack of defects or changes of material within the stone. Ideally, a processed gemin will be only just indistinguishable from colored glass, aside from radiating an intense light, and shimmering in an adamantine luster. Voids and imperfections within a stone should be removed during cutting, especially for sensitive instruments, or for Setting a stone in the creation of Keygemin.
Voids, defects, cracks, bubbles, and non-homogeneous material is better removed because the size of a gemin does not necessarily improve a gemin's performance, or a Keygemin's ability to set. In most cases a Keygemin would prefer it's gemstone to be cut and polished, than a be a larger, rougher stone. Removal of gemstone defects is effectively grooming of a Keygemin, and is an expected part of its care.
Clarity is graded in two classes. The first is "clear", a clear gem is one that has no obvious imperfections over a short period of visual inspection. A clear gem is the most common grade of processed gemin, and clear grade is an expected result from any rudimentary gemin processing service. The second is "graded" followed by a number 0 through 12. 0 indicates a lower standard of clear gemin, which is either expended of useful energy, or unable to undergo the Keygemin setting process. A grade 12 gemin has very few, if any, visual imperfections. Even upon magnified inspection of the gemin in detail, by any professional. Grading of a gemin can take several bars, about two and a half hours, and it should be expected that in most cases a result of gem grade 1 or 2 will be received.
Any gemin that has been inspected to include fracture, or streaking of other material, or have a poor transparency are typically graded 0, 1, or 2. Low graded gems are better used for industrial applications, or set to be Keygemin to perform labor or to become household pets. Gemin of higher grades can be sold to merchants or to the local government, to be used in military applications. They can of course be set to become powerful Keygemin, useful for a number of tasks.
Cut for gemin, compared to a gemstone on Earth is a strange case. The goal in gemcutting for gemin is to make the largest. most spherical shape of gemin while removing as many voids or defects in the material as possible. This is to maximize its power per size ratio. While gemcutting for gemin jewelry would follow the normal guide of making many facets or reflective surfaces, cutting of a gem for the utility of extracting power or getting work out of a stone, a spherical shape is most efficient.
The only major exception to this rule is for the setting of Keygemin. Keygemin are vain creatures that prefer their stones to be vibrant and pleasing to both themselves and to others. Keygemin typically dislike the spherical shape of processed gemin stones, and would prefer to be cut at sharp geometric angles. The most efficient shapes for setting Keygemin are the plutonic solids; tetrahedron, cube, octahedron, dodecahedron, and icosahedron. Other uniform convex polyhedra like cuboctahedron, icosidodecahedron, truncated polyhedra, or prisms may also be preferred depending on the personality of the Keygemin. Keygemin are best faceted when their gemin's cuts are approximating a sphere. As this better utilizes the gemin's available power.