Houston Jewelry Appraisal and Repair

Gemstone Observation

GEMSTONE
SPECIES & VARIETY

GENERAL OBSERVATION

Most Jewelers and Gemologists are good at General Observations of a Gemstone. However, it is the obvious characteristics of a gemstone that can mislead you sometimes while making an identification claim.

See below what gemstone traits to look for when assessing the general appearance of a Colored Stone.

Shape and Color

At first glance, a gemstone's Shape and Color are the most notable. Identifying gems begins with Color. The Color can immediately eliminate other gems it may be.

Shape is also straight forward, when regarding a gemstone, it is always important to communicate its Shape.

Cutting Styles

Here are four main cutting styles used in the market for Colored Stones.

● Brilliant Cut: A stone that is manufactured using bezel (kite) and Triangular facets producing more Fire.
● Step Cut: A cut that emphasizes Symmetry. These cuts involve using rectangular and square facets.

● Checkerboard Cut: A Designer's Cut producing many diamond shaped facets resembling a checkerboard.

● Cabochon Cut: A rounded dome Cut with a flat bottom in various shapes.

Phenomena

Does a gem display a very unusual trait? These characteristics are referred to as Phenomena. The image shows:

● Opals play of color;

● Pearls orient,

● moonstones Adularescence

● Sapphires Asterism

There are others, this is just an example of Phenomena.

Transparency

Above are samples of Transparent, Translucent, and Opaque Gemstones. A stone is considered transparent when light passes through it. Translucent gems transmit some light, where as Opaque stones reflect it. Opaque gemstones do not allow light to pass through.

Dispersion | Fire

Dispersion produces what most people know as "Fire." This happens when white light enters the gem and and exits. White light rays refract and are bent as they exit the stone. This separates it into a multitude of spectral colors and delivers Fire.

GEMSTONE SPECIES | VARIETY

Colored Stones are classified according to Gemstone Species. Within these Species are Varieties.

● A Gem's Crystal Structure and Chemical Composition defines it's Species.

● The Gem Species Corundum is a trigonal crystal system and is a Chemical Composition of Aluminum Oxide (Al2O3).

● When small Trace Elements combine with Corundum, we get different Varieties such as Ruby and Blue Sapphire.

See the example below.

Gem Species: Corundum = Aluminum Oxide

Gem Variety: Blue Sapphire =

Aluminum Oxide + Iron & Titanium Trace Elements.

Gem Variety: Ruby =

Aluminum Oxide + Chromium Trace Elements.

The trees shown represent the individual Gem Species (gemstone families.) Certain Varieties are listed that belong to each family. Mind you, this is only a fraction of minerals in the market.