Assignment 12 - Ruby Flashcards
What are the qualities of the finest ruby color?
The finest ruby has a pure, vibrant red to slightly purplish red hue.
As the hue becomes orangy or more purplish, the ruby moves down the quality scale into good and commercial ranges.
The highest-quality rubies have vivid saturation.
What makes a ruby red?
The trace element chromium causes rubies to be red, and can also cause fluorescence, which intensifies bodycolor.
The finest rubies typically form in
marble deposits.
What factors influence a cutter’s fashioning decisions?
Ruby rough is very expensive, so cutters try to conserve as much weight as possible. They might fashion flattened ruby rough into shallow stones
even though light escapes through flattened pavilions, causing unwanted windowing.
Pleochroism is another factor that influences cut. Pleochroism in ruby typically appears as red to purplish red in one crystal direction and orangy
red in the other. Cutters can minimize the orangy red color by orienting the table facet perpendicular to the crystal’s optic axis.
What are ruby’s typical clarity characteristics?
Inclusion-free rubies are practically nonexistent, so people in the trade expect rubies to have at least some inclusions. Typical ruby clarity characteristics include silk (rutile needles), boehmite needles, included crystals, fingerprint inclusions, growth zoning, and color zoning.
How do ruby’s clarity characteristics affect value?
Inclusions can have positive or negative effects on a ruby.
One positive is that they can help to separate a treated or synthetic stone from an untreated, natural one.
Some inclusions can actually contribute positively to a gem’s appearance. The presence of rutile silk causes light to scatter across facets that might
otherwise be too dark. This adds softness to the color and spreads the color more evenly across the ruby’s crown.
If large and prominent inclusions are located under the table facet, they greatly diminish the transparency, brilliance, and value of the stone. Inclusions can also limit a ruby’s durability.
What are the most common ruby treatments?
- Heat treatment (very common)
- Flux Healing
- Lattice Diffusion
Why is disclosure of ruby treatments important?
Since all treatments affect value, they should all
be disclosed. Non-disclosure can lead to a lack of consumer confidence,
which will depress the market for any gem, including ruby.
Which treatments can deteriorate over time?
Clarity enhancements like glass filling, oiling or dyeing.
Where are the world’s major ruby sources?
African sources have replaced the more traditional Southeast Asian ones, and now supply the majority of the world’s ruby, with Mozambique the most significant producer.
In Southeast Asia, production comes from Myanmar and Vietnam and to a lesser extent from Sri Lanka and Cambodia.
Central Asia also supplies ruby from Tajikistan, Afghanistan, and Pakistan, but the mining is far more difficult than in Africa and there are often
challenging political and safety issues.
Where are the largest ruby-consuming markets?
The largest ruby-consuming markets are the US, China, Japan, the European Union, and—for high-end stones—the Middle East and auctions in Switzerland.
How have changes in the world economy reshaped the ruby market?
Africa has replaced Southeast Asia as the
source of the majority of the world’s ruby. The Montepuez area of Mozambique has emerged as the world’s most important ruby source.
What was the role of imitation and synthetic rubies in the market?
Introduction of the first synthetic rubies destabilized the natural gem market until detection methods were established.
What are some of the materials used as ruby imitations?
Imitations for the translucent-to-opaque ruby used to produce cabochons, beads, and carvings include near-colorless stones such as quartz, which can be quench-crackled and dyed. Aggregate minerals such as beryl or white or pale-colored gems can also be dyed to imitate low-quality ruby. Other dyed gem materials, including corundum, have also been used.
What are the main processes used to grow synthetic ruby?
Ruby is being synthesized using both melt and solution processes.
While it can take hours or days to make flame-fusion ruby, the more complex solution processes can take weeks or months, adding to the cost
of the product. These methods imitate natural ruby formation more closely than melt processes, so the resulting materials have inclusions and growth structures that look more natural.
What factors led to market acceptance of synthetic ruby?
Cost on one hand and more natural looking synthetics on the other hand.
