Chalcedony Gemstone

Color

Some of the most common types of chalcedony are:
Bloodstone: a dark green chalcedony with deep red spots
Agate: curved or angular-banded varieties of chalcedony
Chrysoprase: translucent to semi translucent, light to medium yellowish green
Onyx: larger slabs of straight parallel layers of different colors

 

 

Clarity

Chalcedony is a gem composed of cryptocrystalline (microscopic) quartz crystals that form in tightly interlocking, fibrous masses. All chalcedonys are semi-translucent to opaque but rarely will eye-clean cut stones be cut form it

Cut

Chalcedonies may be porous, so care must be taken not to immerse the gem in substances that could change its appearance
Use damp, soft cloth, or scrubbing with a soft-bristle toothbrush
Chalcedonies possess an extraordinary toughness, allowing them to be carved in large flat cabochons, intaglios, cameos, tablets or even plates or bowls. Idar-Oberstein, twin cities in Germany, have been known for developing the cutting and carving industry for this gem since the 1700s.

Treatment

Dyeing: chalcedony can be dyed in practically all colours, due to its porous nature. Much of the black chalcedony sold on the market is dyed black. In banded material, some bands may be dyed while others remain white.
Heating: some yellow to brown material may be heat treated to result in redder colours.

Care

Chalcedonies may be porous, so care must be taken not to immerse the gem in substances that could change its appearance. As with most gems, a damp, soft cloth, or scrubbing with a soft-bristle toothbrush, are the best ways to clean these two forms of quartz.
Chalcedony exhibiting unusual banding or landscape scenes are particularly prized, as are agates containing dramatic dendritic inclusions. Iris agates and fire agates exhibiting strong iridescent colours are also collected. Finally, carved chalcedony, such as intaglios or cameos, may be collectible if they have provenance that can be identified as typical of a certain era. Signed gems from a known lapidary artist are also collectible.

Beryls Gemstones

Color

Red: Bixbite, only found in one location in Wah Wah Mountains, Utah, USA

Bright yellow: Heliodor. If yellow becomes deep toward orange: "golden Beryl"

Colorless: Goshenite

Deep blue: only found on one location in Brazil: will quickly loose its color if expoed to daylight

Green: too light to be considered emeralds. Problematic as a green beryl is much cheaper than an emerald but sometimes still sold as one

Clarity

Considering the range of beryls clarity can vary from eye-clean to very included

Cut

Beryls may be cut several different ways, though emerald cut and oval cut gems tend to predominate

Treatment

Color: Heating can take out a secondary color rendering a deeper, more saturated color
Color: Sometimes colorless beryls are irradiated to produce yellow colours. This colour is considered stable. Maxixe beryl is almost always irradiated is often irradiated in a laboratory. Color is not stable. Some colourless and light pink beryl from Minas Gerais is irradiated to produce maxixe beryl
Clarity: colourless oil and resins are sometimes used to hide fissures in red beryl

Care

Beryls are generally quite hardy unless they are strongly includedRed beryls tend to be more like emerald in this respect and may be fragile if the gem has many surface reaching fissures. A dampened, non-abrasive cloth is best used to clean beryl jewelry.
Large beryls with high level of saturation
Rare beryls such as Red beryl
Special effects such as "cat's eye"
Borderline beryls: "is it an emerald or is it a green beryl"

Color

Different varieties: purple is a rare variety from Maine. Blue stones from Brazil with colors rivalling Paraiba tourmaline are most in demand
A light green variety of apatite carries the trade name "asparagus stone"
The recent availability of the neon blue-green variety from Madagascar has gained popularity

 

 

Clarity

Eye clean larger stones are quite common

Cut

Cabochon or creative cut by lapidary artists

Treatment

Color: Most apatites are heat treated to enhance color

Care

Apatites are delicate - especially when subjected to heat, temperature changes, changes in air pressure (such as in an airplane)
Dampened soft fabrics with no abrasive or chemical additives, or a soft bristle toothbrush doused with water
Not recommended to use in rings

Aquamarine Gemstone

Color

Main colors: greenish blue to blue green
Light in tone and transparent
Some milky quality if lots of inclusions
Most collectible colors: aquamarines that have saturated, light blue colours are especially desirable, though a few beryl collectors prefer a slight greenish tinge

Clarity

They frequently possess a vitreous clarity not found in emeralds. For this reason, aquamarines may be fashioned as exceptional clean gems and carvings
Lower grade aquamarines can have a milky appearance if the crystal has a lot of inclusions
a potentially desirable "cat's eye" effect occurs when miniscule, hollow growth tubes form parallel to one another

Cut

Relatively large stones can be cut due to its hardness and relatively large crystals (up to hundreds of carats) without inclusions
Unusually cut gems are also popular, especially in gems that have been fashioned by an important lapidary artist.
Aquamarines and other beryls often lend themselves to sculptures because of their size

Treatment

Consider every aquamarine heat treated
Heat treatment causes them to loose their secondary greenish color and create a more "aquamarine blue" gem
It is generally impossible to gemologically determine whether an aquamarine has been treated or not

Care

Aquamarine can be worn in jewelry under normal use. Larger aquamarines should be worn with care, especially in settings such as rings that can be easily knocked
Cleaning: sudsy water and damp cloth

Most collectible:

Saturated, light blue colours
Gems that have been fashioned by an important lapidary artist or cut in unusual ways
Aquamarines from desirable localities, such as Santa Maria aquamarines from Itabira, in Brazil, are collectible in accordance to their legendary depth-of-colour

Ametrine Gemstone

Color

In ametrine, a unique form of quartz mined from a single locality in Bolivia, the colours are both yellow and purple in areas of zoning

Clarity

Ametrine, just like most crystalline quartzes is often eye-clean

Cut

Ametrine can also be cut to blend the two colors so that the resulting stone is a mix of yellow, purple, and peach tones throughout the stone
Ametrine is most typically faceted in a rectangular shape with a 50/50 pairing of the two colors
Sometimes a checkerboard pattern of facets is added to the top to increase light reflection
Ametrine is also popular among artistic cutters and carvers

Care

Because the bi-coloured ametrine comes from only one mine in the world, it is sometimes collected if the depth of colour and the division of colour is strong, or if it has been skillfully or cleverly carved.

Amethyst Gemstone

Color

Transparent to translucent lilac to purple through bluish purple
A reddish purple colour-shift that is sometimes visible in incandescent light
In ametrine, a unique form of quartz mined from a single locality in Bolivia, the colours are both yellow and purple in areas of zoning. Such gems are sometimes cut in a way that mixes the colours, and at other times to show the division of colours

Clarity

Some amethysts have liquid inclusions containing solids and gases (water bubbles)
Some minerals suchas rutile and hematite can be found in amthyst as well

Cut

Amethyst can be found in many sizes and therefore offered in many different kinds of cuts and carvings
Many famous lapidaries (cutters) work with amethysts to make unusual carvings or cuts, which are also highly prized.
Bi-coloured ametrine has been skillfully or cleverly carved to emphasize the bi colored nature of the stone

Treatment

Amethysts are heat treated to improve an overly dark purple color or to get rid of the smoky color
Many amethysts in the market are synthetic. It is virtually impossible to differentiate the two

Care

Care should be taken not to knock the gem during use, as small fissures or cracks may develop, especially along facet junctions. It can be cleaned with warm, sudsy water or a dampened cloth. Some amethysts may lighten in tone over time upon prolonged exposure to bright light.
Collectors of amethyst look for depth of the purple colour with red flashes if the gem is cut conventionally. Many famous lapidaries (cutters) work with amethysts to make unusual carvings or cuts, which are also highly prized. Because the bi-coloured ametrine comes from only one mine in the world, it is sometimes collected if the depth of colour and the division of colour is strong, or if it has been skillfully or cleverly carved.

Amber Gemstone

Color

May be seen in yellow, orange and brown colours and rarely as blue and green.
Impurities and organic substances cause colours in amber.
Green and blue ambers are so perceived due to strong fluorescence in some amber from the Dominican Republic

Clarity

Amber often possess gas bubbles which vary in size and quantity within each piece. In the space between the bubbles, the resin is clear
The bubble inclusions actually interfere with the passage of light through the amber, resulting in the dilution and variation of color and opaqueness. For example, there are so many bubbles in milky amber, when examined under the microscope, it resembles sea foam – thus causing the solid milky color.

Cut

Most amber is fashioned as cabochons or rounded or free-form beads, and are rarely faceted

Treatment

Heating in oil causes some cloudy amber to clarify, or to produce darker amber colours
Amber is sometimes dyed to add a darker tone to lighter materials
Two factors that affect the color of amber is air and the actual tree source

Care

While rings using amber are used, the user must take special care
Avoid rough handling, heat and chemicals for all amber
They are soft, occasionally brittle, and porous enough to be attacked by acids
Cleaning may be performed using a dampened cloth or a moistened soft bristle toothbrush
Strong colours in amber are considered collector items, as is any amber containing unusual insects. Entomologists seeking to understand a bygone world often collect these amber samples for further study.