- Explain the color-changing ability of alexandrite that is hard to find in other forms, and what type of mineral it is.
Alexandrite has a color-changing property, showing a bluish-green shade in daylight and a purplish-red shade under incandescent light. It is also known as the “magic trick of nature” and is the color-change type of the mineral chrysoberyl. - What is an opal physically made of, and how do we get the play-of-color of an opal by means of this arrangement?
Opal consists of microarrays of stacked silica spheres. This structure diffracts light, splitting it into a fire of flashing, kaleidoscopic colors —a phenomenon that helps value the gem. - Define the connection between ruby and sapphire and distinguish what mineral species they are and what trace element makes ruby appear to be of a different color.
Both ruby and sapphire are varieties of the mineral corundum. The red variety, ruby, is colored by traces of chromium. The name sapphire applies to any other color of corundum. - What is amber, and what special feature does it have that qualifies it to be a time capsule?
Amber is a fossilized tree resin, usually orange or golden brown. It is described as a time capsule because it preserves traces of life that existed millions of years ago, such as insects, leaves, scorpions, and lizards. - Name the three predominant minerals that make up the rock Lapis Lazuli, and the country that is believed to produce the best specimens.
Lapis Lazuli is an aggregate rock composed of many minerals, of which the major ones include lazurite, calcite, and pyrite. Afghanistan is considered the source of the highest-quality lapis. - What is the process of pearl formation, and where are they available in nature?
Pearls are organic gems formed inside the bodies of marine and freshwater mollusks. They may form naturally or be carefully cultivated by humans. - What is the name of the gemstone that is referred to as the great imposter, and why did it acquire this name?
Spinel is called the great imposter because, over the centuries, it was used to replace ruby in many crown jewels of Europe. Well-known large spinels mistaken for rubies include the “Ruby of the Black Prince” and the “Timur Ruby.” - There is only one place on earth where tanzanite is located. Identify the place and species of mineral to which tanzanite belongs.
Tanzanite is found only near Mount Kilimanjaro in Tanzania. It is the blue-violet or purple variety of the mineral zoisite. - What is ametrine, and what are the two gems united in one crystal to make it?
Ametrine is a rare form of quartz. It is distinct because it combines the colors of two other types of quartz—amethyst (purple) and citrine (orange-to-yellow)—in a single crystal. - List three different types of gemstones of the mineral called beryl used in the source material.
The mineral beryl is found in three gemstone varieties: emerald (bluish-green to green), aquamarine (blue to slightly greenish-blue), and morganite (pink to orange-pink).
Essay Questions
- Compare and contrast mineral species of beryl, quartz, and corundum.
Describe at least two different varieties of gemstones of each species listed in the reading (note two different colors of that stone), and explain with reference to trace elements that make them appear various. - The passage describes several gemstones that exhibit optical phenomena.
As examples, opal, moonstone, sunstone, and so on, explain what visual effect each gem produces (e.g., play-of-color, adularescence, aventurescence) and why it does this, as detailed in the source. - Discuss the historical and cultural meaning of at least three types of gemstones.
Examples may include emerald, ruby, jade, or turquoise, investigating how these gems have been treasured and used by various civilizations. - Trace elements and microscopic inclusions in gemstones
Discuss how these factors can affect the eventual appearance of a gemstone. Give examples from the text, such as morganite, rose quartz, ruby, and citrine. - Garnet group varieties
The garnet group is a closely related group of minerals. Elaborate by analogy to other mineral species with more than one variety, such as beryl or feldspar, and discuss the variety of colors found in the garnet group.
Glossary of Key Terms
- Adularescence: Light scattering by microscopic alternating layers causes a billowy blue sheen that flows under a gem’s surface. This is the most important optical property of moonstone.
- Alexandrite: The color-change form of chrysoberyl, bluish-green in daylight and purplish-red under incandescent light.
- Amber: Fossilized tree resin, usually orange or golden brown, known for preserving ancient life forms.
- Amethyst: Purple quartz.
- Ametrine: A very rare transparent quartz combining the purple of amethyst with the orange-yellow of citrine in a single crystal.
- Aquamarine: Blue to slightly greenish-blue variety of beryl.
- Aventurescence: A clear, vivid sparkle observed in sunstone varieties.
- Beryl: Mineral species including emerald, aquamarine, and morganite.
- Chrysoberyl: Mineral species that includes alexandrite.
- Citrine: Clear, light yellow to brownish-orange quartz, colored by iron.
- Cordierite: Mineral known as iolite in the jewelry trade.
- Corundum: Mineral species containing ruby (red) and sapphire (all other colors).
- Diamond: A gemstone composed of carbon, prized for its purity and colorlessness.
- Emerald: The most valued green variety of beryl.
- Feldspar: Mineral group including moonstone and sunstone.
- Garnet: A family of closely related minerals with gemstones in nearly every color.
- Iolite: Jewelry trade name for cordierite.
- Jade: Term for gemstones nephrite and jadeite.
- Kunzite: Pink to violet spodumene colored by traces of manganese.
- Lapis Lazuli: A Rock made of aggregated minerals, mainly lazurite, calcite, and pyrite, prized for its dark blue color.
- Moonstone: Feldspar valued for its rippling blue adularescence.
- Morganite: Pink to orange-pink beryl tinged with traces of manganese.
- Olivine / Peridot: Yellow-green gem variety.
- Opal: Gem with a kaleidoscopic play of color, produced by microscopic silica spheres.
- Pearl: Organic gem formed within mollusks.
- Peridot: Yellow-green variety of olivine.
- Quartz: Mineral species including amethyst, citrine, ametrine, and rose quartz.
- Rose Quartz: Quartz with fine pink color and translucence due to minute mineral inclusions.
- Ruby: Red corundum, colored by chromium traces.
- Sapphire: Non-red varieties of corundum.
- Spinel: Gem with a variety of colors historically confused with ruby.
- Spodumene: Mineral species including kunzite (pink to violet).
- Sunstone: Feldspar exhibiting aventurescence.
- Tanzanite: Blue-violet variety of zoisite, found only in Tanzania.
- Topaz: Gem with a wide range of colors, from honey yellow to ice blue.
- Tourmaline: A Gem known for a large variety of colors.
- Turquoise: Copper phosphate gem, rare, deep blue known as azure or robin’s egg.
- Zircon: Gem with high refraction and fire, distinct from synthetic cubic zirconia.
- Zoisite: Mineral species of which tanzanite is a blue-violet variety