The chemistry, properties and tests of precious stones

Metadata

Gutenberg ID

23626

Title

The chemistry, properties and tests of precious stones

Language

en

Book source

Project Gutenberg

Description max 80 words

This authoritative handbook explores the chemistry, physical properties, and identification tests of precious stones. Written for experts and collectors, it demystifies mineralogy by explaining how rarity, hardness, color, and light interaction define gem value. The text offers practical scientific methods to distinguish genuine gems from imitations, covering topics from crystal structure to pyro-electricity.

Summary up to 500 words

John Mastin's *The Chemistry, Properties and Tests of Precious Stones* serves as a definitive scientific guide to the nature, origin, and identification of gemstones. Mastin begins by challenging the notion that a stone's value is intrinsic; instead, he argues that 'precious' is a comparative term dependent on rarity and market demand, noting how historical shifts in supply, such as the discovery of diamonds, have altered the hierarchy of gem value. He establishes that true precious stones must possess specific physical qualities: they must resist chemical decomposition, withstand wear and heat, and maintain their beauty under light exposure. The work systematically explores the geological origins of gems, explaining that they are not composed of rare metals but are formed from common earth elements through the slow chemical action of water, decay, and immense earth pressure over millions of years. Mastin details the process of percolation, where moisture carries dissolved salts deep into the earth, eventually crystallizing under heat and pressure to form natural jewels. A significant portion of the text is dedicated to physical properties, including crystalline structure, cleavage, color, hardness, specific gravity, and heat conduction. Mastin provides comparative data on how different stones refract light and conduct heat, emphasizing that while light is the primary test for beauty, heat properties vary significantly based on crystalline structure and impurities. He investigates magnetic and electric influences, describing phenomena like pyro-electricity in tourmaline, where heating the stone induces polarity. He distinguishes between magnetic and non-magnetic minerals, explaining that iron content often dictates magnetic responsiveness, a key factor in detecting fraud. Practical testing methods are emphasized throughout. Mastin suggests using pith balls or electroscopes to detect electrical charges and heating stones to observe color changes or water loss, as seen with turquoise. The book also addresses the cutting and polishing of stones, explaining how facets enhance light play and how cutters manage waste. Finally, the text covers various stone types, including diamonds, rubies, sapphires, opals, and imitations like paste, providing chemical compositions and specific tests to verify authenticity. Ultimately, the work aims to preclude fraud by fostering an intelligent understanding of mineralogy among both experts and the general public, transforming mere curiosity into informed appreciation.

LLM editorial rating

4.2/5

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Categories

• Science