History of Gemmology and Gemstones

Questions and Answers

What characteristic of gems indicates the distances they may have travelled?

Color variations

Size and weight

Crystal structure

Abraded surfaces (correct)

How are residual gem deposits described?

Glacial

Eluvial (correct)

Alluvial

Volcanic

What is the main objective of the mining techniques described for gem recovery?

Creating tunnels for exploration

Washing gems with chemicals

Separating gems from lighter materials (correct)

Transporting gems to factories

What is the maximum depth for the round or square section pits used in alluvial gem mining mentioned?

50 feet (15 metres) Signup and view all the answers

Which term refers to the gravel that is dug out during the gem mining process in Myanmar?

Byon Signup and view all the answers

Who wrote one of the first gemstone books in English?

Thomas Nichols Signup and view all the answers

What operation is commonly used to separate gems from gravel in alluvial mining?

Panning Signup and view all the answers

Which mining method is NOT mentioned as part of the diamond mining process?

Surface mining Signup and view all the answers

In what year did the first attempt at gemstone synthesis occur?

1837 Signup and view all the answers

What was a significant outcome of Sir Arthur Church's experiments in 1866?

Discovery of absorption bands in gemstones Signup and view all the answers

What happens to the lighter gravel content during the washing operation described?

It is filtered out. Signup and view all the answers

Which town was named after the British Secretary for the Colonies in 1873?

Kimberley Signup and view all the answers

What was a characteristic of the first synthetic rubies produced by Edmond Fremy in 1877?

They were small and costly to create. Signup and view all the answers

What new gem variety was discovered in 1878?

Green demantoid garnet Signup and view all the answers

What was the significant contribution of Basil Anderson in 1932?

Comprehensive study of gemstone spectra Signup and view all the answers

What was a notable feature of the 'Geneva' rubies that appeared in 1885?

They contained bubbles, proving them to be synthetic. Signup and view all the answers

What is the characteristic feature of an axis of symmetry in a crystal?

It allows the crystal to appear multiple times during rotation. Signup and view all the answers

What is the role of the plane of symmetry in a crystal?

To divide the crystal into two mirror-image halves. Signup and view all the answers

What is the highest order of symmetry associated with the cubic crystal system?

Isometry Signup and view all the answers

How is a centre of symmetry defined in relation to a crystal?

It denotes a point with equal faces and edges on opposite sides. Signup and view all the answers

What is characteristic of the crystal axes in the cubic system?

They are of equal length and intersect at right angles. Signup and view all the answers

Which type of symmetry does a cube have relating to its planes?

Nine planes of symmetry. Signup and view all the answers

Which term describes axes of symmetry that may be classified as diagonal, trigonal, tetragonal, or hexagonal?

Classification of axes Signup and view all the answers

What color is specifically designated to Rubies?

Red Signup and view all the answers

Which mineral possesses a prismatic habit and lacks basal cleavage?

Danburite Signup and view all the answers

Which variation of Sapphire is noted for its barrel shape?

Spindle Shape Signup and view all the answers

Which mineral system does Diamond belong to?

Cubic Signup and view all the answers

Which of the following colors is not a color associated with Diamond?

Orange Signup and view all the answers

Which mineral is recognized for displaying horizontal striations?

Sapphire Signup and view all the answers

What is the unique characteristic of Microcline among its varieties?

Green color of Amazonite Signup and view all the answers

Fluorite is classified under which crystal system?

Cubic Signup and view all the answers

Which characteristic is distinctive of Rhombohedron forms?

Growth Marks Signup and view all the answers

What color is Plagioclase Feldspar known to exhibit?

Multi-colour Signup and view all the answers

Which material is described as a mineraloid despite resembling a mineral?

Opal Signup and view all the answers

What characterizes the arrangement of atoms in crystalline materials?

Ordered and symmetrical lattice Signup and view all the answers

What is the primary factor that influences the physical characteristics of crystalline materials?

Orientation of the crystal Signup and view all the answers

In crystal symmetry, what does the axis of symmetry represent?

An imaginary line for rotation Signup and view all the answers

Which of the following is NOT a characteristic of the cubic crystal system?

Lowest order of symmetry Signup and view all the answers

What is crystallography primarily concerned with?

The science behind crystal structures Signup and view all the answers

Which property varies with direction only in crystalline materials?

Hardness Signup and view all the answers

What shape is typically associated with the tetragonal crystal system?

Rectangle with square ends Signup and view all the answers

Which of the following statements about man-made glass is true?

It has a disordered atomic arrangement. Signup and view all the answers

How many planes of symmetry does the cubic crystal system have?

9 Signup and view all the answers

What happens during the crystallization of materials from molten solutions?

Large well-shaped crystals form. Signup and view all the answers

What defines the c-axis in a crystal system?

The vertical axis Signup and view all the answers

What type of symmetry is indicated by a mirror plane?

Plane of symmetry Signup and view all the answers

Which crystal system is identified by having axes of symmetry amounting to 5?

Tetragonal Signup and view all the answers

Study Notes

Gemstone History and Development

Thomas Nichols authored one of the earliest gemstone books in English in 1652.
Gemmology developed as a specialized field from mineralogy in the late 19th century.

Milestones in Gemstone Synthesis and Study

In 1837, Marc Gaudin synthesized small ruby crystals using potassium aluminium sulfate and potassium chromate.
The 1800s saw a surge in crystalline substance reproduction, including utilizing lower melting point solvents.
Sir Arthur Church discovered absorption bands in Ceylon zircons and almandine garnets using an early spectroscope in 1866.
Basil Anderson conducted a comprehensive spectrum study of gemstones for identification in 1932.
The South African diamond rush began after Church's findings, with 5,000 diggers active on the Vaal, Modder, and Orange rivers.
Kimberley, named after the Earl of Kimberley, emerged in 1873 due to diamond mining activity.
Edmond Fremy created the first synthetic rubies of commercial quality in 1877, but production was costly and the crystals were small.
The discovery of green demantoid garnet marked a notable new gem variety in 1878.

Gem Formation and Transportation

Gem deposits are categorized by their locality, influenced by geological conditions favoring gemstone formation.
Evidence indicates the distances traveled by gems from their parent rocks can lead to unique surface characteristics, such as water-worn topaz.

Mining Techniques

Gem recovery methods vary from manual techniques to advanced mechanized operations.
In Myanmar and Sri Lanka, miners excavate pits up to 15 meters deep to reach gem gravel.
Dense gem material is separated from lighter sand using a hand-washing technique in woven baskets.
Diamond mining employs varying methods from simple panning to extensive open-cast operations.

Crystal Symmetry and Axes

Crystal identification relies on the analysis of symmetry and axes of symmetry, which include:
- Axis of symmetry: Imaginary lines indicating how many times a crystal's profile appears during a full rotation.
- Plane of symmetry: An imaginary plane dividing a crystal into mirror-image halves.
- Centre of symmetry: When crystal faces occur identically across a central point.

Seven Crystal Systems

Crystals organize into seven systems based on symmetry and crystal axes:
- Cubic (Isometric): Highest symmetry with three equal axes intersecting at 90°. Common forms include cube and octahedron.
- Tetragonal: Two equal lateral axes with the c-axis at 90° and differing lengths.

Properties of Crystalline Materials

Crystalline materials are defined by their structured atomic arrangements and exhibit properties varying with crystal orientation.
Notable properties include hardness, cleavage, color, and optical effects, which can fluctuate by direction.
Crystallography studies the arrangement and behavior of atoms in crystal forms.

Common Gem Varieties and Their Characteristics

Ruby: Red corundum variant; growth habits include triangular and tabular forms.
Sapphire: Any corundum color except red; features variable shapes and growth marks.
Danburite: Orthorhombic system; found colorless, yellow, or brownish.
Diamond: Cubic system; presents in various colors including colorless, yellow, and rare pink or red.
Feldspar: Includes varieties like transparent Adularia, yellow Moonstone, and multi-colored Labradorite.

Notes on Man-made and Natural Materials

Man-made glass lacks the symmetrical atomic arrangement seen in natural gemstones due to rapid cooling processes.

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Description

Explore the fascinating evolution of gemmology from its early days in the 17th century to significant advancements in the 19th century. This quiz highlights key milestones in the study of gemstones, including early literature and technological breakthroughs. Test your knowledge about the important figures and developments in the field of gemmology.