Everand Logo

Welcome to Everand!

  • Discover millions of ebooks, audiobooks, and so much more with a free trial

    From $11.99/month after trial. Cancel anytime.

    Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing
    Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing
    Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing
    Ebook54 pages1 hour

    Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing

    By Read Books Ltd.

    3/5

    ()

    Read preview

    About this ebook

    This book contains classic material dating back to the 1900s and before. The content has been carefully selected for its interest and relevance to a modern audience. Carefully selecting the best articles from our collection we have compiled a series of historical and informative publications on the subjects of gemology and crystallography. The titles in this range include "Gemstone Manufacturing" "The Optical Properties of Gemstones and Crystals" "The Thirty-Two Classes of Crystal Symmetry" and many more. Each publication has been professionally curated and includes all details on the original source material. This particular instalment, "Testing the Colour of Gemstones" contains information on the dichroscope, filters, lenses and much more. Intended to illustrate the main aspects of colour testing it is a comprehensive guide for anyone wishing to obtain a general knowledge of the subject and to understand the field in its historical context. We are republishing these classic works in affordable, high quality, modern editions, using the original text and artwork.
    LanguageEnglish
    PublisherRead Books Ltd.
    Release dateMay 31, 2013
    ISBN9781473390577
    Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing

    Related to Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing

    Related ebooks

    Science & Mathematics For You

    View More
    View More

    Related podcast episodes

    Related articles

    • UNLIMITED

      The Making Of A Silversmith

      May 31, 2020

      The Making Of A Silversmith
      2 min read

    • UNLIMITED

      Bead Search

      Jul 30, 2021

      Bead Them Up’s customers have been very impressed with the range and quality of beads available, and they even more impressed when they see Bead Them Up’s magnificent ground floor showroom at their new location in Ramsgate, in the southern suburbs of

      5 min read

    • UNLIMITED

      Eye For The Precious

      Jun 7, 2019

      Eye For The Precious
      3 min read

    • UNLIMITED

      As Nature Intended

      May 17, 2023

      As Nature Intended
      2 min read

    • UNLIMITED

      Know Your Diamonds

      Dec 23, 2019

      Know Your Diamonds
      5 min read

    • UNLIMITED

      A Metal With Magical Powers

      Jul 14, 2023

      A Metal With Magical Powers
      3 min read

    • UNLIMITED

      Quartz

      Jan 19, 2023

      Quartz
      4 min read

    • UNLIMITED

      Wonders Of The Lycurgus Cup

      Oct 28, 2021

      Wonders Of The Lycurgus Cup
      1 min read

    • UNLIMITED

      Inside Out

      Oct 2, 2023

      Inside Out
      7 min read

    • UNLIMITED

      Ask a Pirate

      Sep 1, 2023

      Ask a Pirate
      4 min read

    • UNLIMITED

      Colour

      Dec 1, 2023

      Colour
      4 min read

    • UNLIMITED

      Proud To Be An Aussie!

      Jul 28, 2022

      Proud To Be An Aussie!
      5 min read

    • UNLIMITED

      Prying Apart Colors

      Nov 1, 2021

      Prying Apart Colors
      3 min read

    • UNLIMITED

      A Fluorescent World

      Sep 10, 2018

      A Fluorescent World
      4 min read

    • UNLIMITED

      Rock stars: CRYSTAL CLARITY

      Apr 5, 2023

      Rock stars: CRYSTAL CLARITY
      3 min read

    • UNLIMITED

      Colour Me Envy

      May 3, 2023

      Colour Me Envy
      4 min read

    • UNLIMITED

      All The Reds, Blues, And Greens

      May 10, 2024

      The study of ancient pigments developed with the modern science of chemistry. Already in the eighteenth century, the discovery of paintings and cakes of pigment at Pompeii inspired investigations of ancient pigments. Researchers today can use a varie

      6 min read

    • UNLIMITED

      Rainbow Vibes

      Aug 2, 2022

      Rainbow Vibes
      1 min read

    • UNLIMITED

      Agate

      Jul 13, 2023

      Agate
      4 min read

    • UNLIMITED

      Being Crystal Clear

      Dec 1, 2023

      Being Crystal Clear
      4 min read

    • UNLIMITED

      Garnet

      Sep 27, 2018

      Garnet
      5 min read

    • UNLIMITED

      Garnet

      Nov 24, 2022

      THE NAME GARNET actually refers to a group of chemically and physically similar minerals. The name was derived from the Latin word granatum (meaning grain), which may have been taken from Punica granatum (pomegranate), as small, red garnet crystals w

      5 min read

    • UNLIMITED

      Block Of The Month

      Feb 24, 2022

      Block Of The Month
      2 min read

    • UNLIMITED

      Exhibitions

      Mar 2, 2018

      Exhibitions
      9 min read

    • UNLIMITED

      Space-age Sparkle

      Jul 27, 2020

      Space-age Sparkle
      2 min read

    • UNLIMITED

      Defining Problem Coins: Part II

      Aug 30, 2024

      The characteristics we see on our coins offer clues to their condition. As with most things concerning coins, they occur in various degrees of severity. In this column, from the perspective of a non-chemist, I’ll write about cases where some oxidized

      2 min read

    • UNLIMITED

      Red Light Field Test

      Jul 10, 2019

      Red Light Field Test
      7 min read

    Reviews for Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing

    3/5

    1 rating0 reviews

    What did you think?

    Tap to rate

    Review must be at least 10 words

      Book preview

      Testing the Colour of Gemstones - A Collection of Historical Articles on the Dichroscope, Filters, Lenses and Other Aspects of Gem Testing - Read Books Ltd.

      Herbert

      COLOUR, COLOUR FILTERS AND THE

      DICHROSCOPE

      IT HAS OFTEN BEEN STRESSED BY THOSE WHO WRITE about gems that colour is a most unreliable guide in identifying a stone. Such a statement is, of course, to a certain extent true, and the tendency in the past to label (with qualifying adjectives) all yellow stones as topaz, all red stones as ruby, and all green stones as emerald was due to too great an insistence upon the importance of that usually accidental characteristic, colour. Anyone, however, whose job it is to handle and appraise coloured stones knows how a really practised eye can recognize almost all the well-known gems at once by their characteristic shade of colour. Ability to recognize the particular shades exhibited by a given variety can be acquired by anyone with a naturally good colour sense, and developed by practice to a quite astonishing degree of virtuosity. As an instance of this the author can remember, when showing a case of about fifty mixed coloured stones to a group of gemmology students at Chelsea Polytechnic, that one of the students was able to name correctly every specimen at sight, with the exception of one or two rarities such as phenakite and danburite.

      Such knowledge and acute perception of colour are admittedly rare, but for the normal person even if the species still remains in doubt the colour of the stone will have narrowed down the possibilities enormously, especially when the lustre is also taken into consideration.

      Thus, though there are many green stones, several red stones, and several blue, there are few indeed that have the green of emerald, the red of ruby, or the blue of sapphire.

      Against this it must be admitted that the more brownish-red tints seen in Siam rubies are almost impossible to distinguish from certain red garnets and spinels, and that among the pale pink or mauve stones it is very hard for the eye to distinguish between pink topaz, tourmaline, mauve spinel, pale amethyst, kunzite, and pink beryl.

      Often two stones which appear to have precisely similar colours can nevertheless be distinguished on a colour basis if these colours are analysed or sorted by simple instruments.

      To understand how this can be so, we must make a very brief incursion into theory. What we call white light—that is, light from the sun or other incandescent bodies—is composed of a mixture of all the colours of the rainbow. Spin a circular card painted in equal sectors with the bright rainbow colours and the disc will appear white while spinning rapidly.

      Newton, in the year of the Great Fire of London (1666), was the first to show that sunlight has a composite nature, by analysing a narrow beam which passed through a chink in the shutter into his darkened room by the simple expedient of placing a glass prism in the path of the ray.

      Light is variously refracted by a transparent solid according to its wavelength; the red rays, of longer wavelength, being less

      Enjoying the preview?
      Page 1 of 1