Clarity, Cut and Carat Weight Flashcards
What’s the difference between blemishes and inclusions?
A blemish is confined to the surface of the gem, an inclusion is enclosed in the gem or reaches the surface from its interior.
What is an inclusion
Inclusions could be breaks, pockets of fluid, or foreign mineral crystals.
What kinds of inclusions threaten a gem’s durability?
Breaks
Together blemishes and inclusions are called….
Together, blemishes and inclusions are called clarity characteristics, and colored stones display a wide variety of them.
What factors dictate an inclusion’s effect on appearance?
Size: Large inclusions have more influence than small inclusions.
Number: In general terms, the more inclusions a stone has, the lower its clarity. There are exceptions: A stone can have many minute inclusions and still be high on the clarity scale for that species.
Position: Inclusions in the center of the table are usually more visible than those under the bezel facets or near the girdle.
Color or Relief: Inclusions that are close in color to a gem’s bodycolor do not stand out. But an inclusion that contrasts with the gem’s bodycolor, like a red inclusion in a colorless stone, will usually have a greater effect. A break that’s filled with air will also stand out.
What are the different types of breaks
There are three basic types of breaks: cleavage, parting, and fracture.
Cleavage is the most threatening kind of break. It results from vulnerability in a gem’s structure. Because of a gem crystal’s atomic pattern—the way the atoms are linked—it can be weaker in certain directions. Cleavage is a flat break that can have a step-like appearance. Topaz, tanzanite, kunzite, and moonstone tend to cleave. So do diamonds. Once begun, cleavage can easily get worse if the stone is handled or worn carelessly, especially if it’s subjected to accidental blows.
Parting is a break parallel to a twinning plane. Twinning planes are created when a gem’s crystal pattern shifts during growth. Like cleavage, parting is a flat break that reflects basic weakness in the stone’s structure. It can also be created or extended by an accidental blow. You’ll see parting most often in black star sapphires.
A fracture is any break in a gem other than cleavage or parting. Fractures often have a scalloped shape, like the curved breaks in glass. They frequently occur during a gem’s growth or during the mining process. A fracture can occur in almost any gem that’s struck by a hard blow. Fractures reaching the surface of some gems—especially emerald—are often filled with oil or epoxy resin to make them less noticeable.
What is the most common type of fracture? Describe what it looks like.
Conchoidal fracture, which has a curved or scalloped shape.
What is a feather
A specific type of inclusion which is an internal break, it looks soft and feathery.
