Gemlab.UK Gemmological Spectroscopy NEWS
Latest up - date August 2017
Recent additions, amendments and future plans.
Due to various circumstances during the past year I have been unable to update this site. I shall not bore you with details but am pleased to say I am now back on track. As you will see the main pages have been updated in appearance now to conform with my home page as below in September 2016.
I have made some new additions to the Excel files in the SPECTRA DATABASE as follows; -
PINK GEMSTONES - A fine transparent rhodochrosite which was on loan from Alan Hodgkinson is now included in PK2 Pink and orangy pink This is also the topic of discussion in my latest entry in THROUGH MY SPECTROSCOPE
GREEN GEMSTONES - the following pale green gemstones have been added to GN2 Yellowish and greyish green Sapphire AHG232; Chrysoberyl AH; and Zircon GNF0616
Recent additions, amendments and future plans.
NEW HOME PAGE I have designed a new home page which I hope presents a more modern theme for my viewers and will also continue to improve the other main pages.
A GUIDE TO THE SPECTROSCOPE - After several years and various trial versions I have finally launched my CD "A Guide to the spectroscope" This is an animated Microsoft PowerPoint Slide Show which can be controlled by the viewer which enables back tracking to repeat the sequence of the animated images for a more concentrated view. For further details go to; - A GUIDE TO THE SPECTROSCOPE
THROUGH MY SPECTROSCOPE and SPECTROMETER. I have indulged myself and purchased a spectrometer - the Canadian GL Gem. Spectrometer - from which I am able to process and edit the results using the Spekwin32-optical spectroscopy software Version 1.712 by Dr.Friedrich Menges. To see my latest work with this go to ; - THROUGH MY SPECTROSCOPE which is really now also through my spectrometer.
Over a year further on now since my last up-date and only now getting back on track . I have at last finally retired from business and perhaps I can find time to make further progress on my website.
I have made some new additions to the Excel files in the SPECTRA DATABASE as follows; -
RED GEMSTONES - A dark brownish red tourmaline - AH567 has been added to RD1 Dark red
YELLOW GEMSTONES - A yellow glass - YLF0005 has been added to YL1
BROWN GEMSTONES - A golden brown zircon - BNF0822 (possibly heat treated) and a pear shaped cabochon of parisite - BNF0797 have been added to BN1 Light brown (Compare the parisite to the apatite above it)
BLUE GEMSTONES - A greenish blue kyanite - BLF0673 has been added to BL2 Greenish blue
VIOLET and PURPLE GEMSTONES - A violet Taaffite - AH3119; a purple CZ - AHB91 and a violet colour change zircon VccOW have been added to VT - PL Violet and Purple The colour change zircon has a remarkable reverse "Alexandrite type" colour change from violet in daylight to green in tungsten.
Further note on this zircon; -
The unpolarised spectrum of this violet colour change zircon was shown in the entry for February 2011 in THROUGH MY SPECTROSCOPE and now this, together with the spectra of the o-ray and e-ray, are included in my database for comparison. It was these spectra which I used to create the elliptical images in my photograph entitled "Close Encounter" which won the Gem - A Photographic Competition in 2012.
My best wishes go out to all my viewers for a happy, healthy and successful year in 2015. This somewhat belated greeting is mainly due to my transition to Windows 8.1 on a new computer in which my current publishing software is not compatible. So until that problem is resolved, here I am on my old machine on good old Windows XP.
PINK GEMSTONES - A pale pink TAAFFITE has been entered in file PK1 Lilac pink This is recent addition to my collection and although pale in daylight appears a stronger pink in tungsten.
Other entries in the pipeline are an interesting brownish red tourmaline and also more detailed entries of the colour change purple zircon referred to in my February 2011 entry in THROUGH MY SPECTROSCOPE
The final colour group - The colour commonly described as purple merges from violet as it gradually returns to red completing the chromatic circle. I have therefore included gemstones of this colour with violet stones under the heading VIOLET AND PURPLE STONES.
This group has now been added to my SPECTRA DATABASE see Excel File VT - PL Violet and Purple Included in this group is an interesting garnet (See ref. AHB195) kindly on loan from Alan Hodgkinson to whom I acknowledge yet another contribution.
This of course does not complete my database as I plan to continue to insert other entries into the appropriate Excel files according to their colour. I shall also add to the PRINCIPAL COMMERCIAL GEMSTONES and introduce other spectra in topics of interest in the field of spectroscopy.
ALEXANDRITE - The July 2012 entry in THROUGH MY SPECTROSCOPE now has improved images of the alexandrite crystal showing the reference axes and optical vibrations in Fig.1 and Fig.2
VIOLET and PURPLE GEMSTONES - This final section of the gemstone colour groups is in progress and should be completed within the next few months.
Scottish Gemmological association conference 2014
Another successful conference was held in Peebles in the Scottish Borders in May this year.. Thank you to those delegates who attended my Gem Spectroscopy Workshop and I hope you all enjoyed and benefited from your participation. It was good to meet colleagues again from around the world.
SAPPHIRE - The page on Diffraction Spectra of Sapphire has been altered to read BLUE SAPPHIRE Other pages will be constructed to deal with fancy coloured sapphires.
BLUE GEMSTONES Excel file BL1 Blue is now back on line with a more detailed account of the cause of colour in blue sapphires.
BLUE GEMSTONES - The fist group in this colour has been added to my database - see Excel file BL1 Blue This consists of pale to dark blue gemstones with no obvious overtones such as green or violet. Two more groups will follow, these will be Greenish Blue and Indigo Blue.
GREEN GEMSTONES - The title of the first group in this colour previously referred to as GN1 Mid-green has be altered to read GN1Green This again simply consists of pale to dark green gemstones with no obvious overtones such as yellow or blue. Excel file GN3 Bluish green Two more gemstones have been added to this group - a colour change garnet from Madagascar ( Courtesy - Alan Hodgkinson) and a dark green spinel from my own collection.
YELLOW GEMSTONES - A very pale, almost colourless yellow apatite has been added to Excel file YL1
Work on the blue and violet stones continues but had to give way to other priorities during the first part of this year - Where have those six months gone? However during this period I have made additions to the following groups.
ORANGE GEMSTONES - A brownish orange treated diamond (Courtesy - Alan Hodgkinson) has been added to Excel file OR1.
YELLOW GEMSTONES - A yellow remondite (Courtesy - Brian Jackson) has been added to Excel file YL1
GREEN GEMSTONES - A colour change green sapphire from Madagascar has been added to GN3 Bluish green
This stone is the subject for discussion in this month's entry in THROUGH MY SPECTROSCOPE
BROWN GEMSTONES - This group has been added to my database and in order to simplify a search I have condensed it to two Excel files ; -
BN1 Light brown This consists of pale brown to golden brown gemstones with very little overtone other than yellow.
BN2 Dark brown These are the darker browns with a pronounced overtone of green, orange or red.
I have other gemstones in this group which will be added later as I proceed but thought it better to make a start and upload these two files at present.
BLUE and VIOLET GEMSTONES - These two groups will complete the spectrum range in my database. Both are extensive with several overtones to be considered in each one. When will they appear? Well all I can say is "Watch this space!"
PRINCIPAL COMMERCIAL GEMSTONES SECTION; - I have made improvements to some of the spectra images in which resolution had deteriorated through copying to the web. It is also my intention to create new pages for other species and add to existing ones such as the garnet series.
ORANGE GEMSTONES - An attractive orange variety of enstatite has been added to my Excel file OR1.
YELLOW GEMSTONES -A pale brownish yellow enstatite has also been added to Excel file YL1
GREEN GEMSTONES - Also added are a pale green kornerupine to Excel file GN2 Yellowish and greyish green and three more brownish green gems in Excel file GN4 Dark and brownish green which are andalusite, enstatite and sinhalite.
BROWN GEMSTONES - I have completed the gemstone and spectra images for this group and once my supporting information is completed I shall create another Excel file. for Brown Gemstones. This I hope to be ready in the early part of 2013.
GEM - A PHOTOGRAPHIC COMPETITION 2012 - See THROUGH MY SPECTROSCOPE
Seasons Greetings and Best wishes to all my viewers for a
HAPPY AND HEALTHY NEW YEAR IN 2013
from John Harris
GREEN GEMSTONES - While currently working on the brown gemstones I decided that a dark Vesuvianite although distinctly brown in tungsten light (Due to the extraordinary ray dominating the colour) should be more correctly described by it's colour in daylight where it is a dark brownish green. To see how the strong dichroism between the green o ray and the brown e ray affects the appearance of the stone and the spectrum go to GN4 Dark and brownish green
YELLOW GEMSTONES - An interesting zircon has been added to my Excel file YL1 This is very pale brownish yellow stone (Almost colourless) from Myanmar which has retained its strong sharp spectrum even after heat treatment.
ORANGE GEMSTONES - An orange variety of kyanite is now included in Excel file OR1.This specimen is from Loliondo, Tanzania.
BROWN GEMSTONES - This section is still under construction.
WHAT IS AN AUDIO GEMSTONE SPECTRUM ? Find out in the September edition of THROUGH MY SPECTROSCOPE
ALEXANDRITE - I have at last made alterations to this page to show the Russian cut stone in daylight and tungsten light and a synthetic alexandrite in fluorescent mode.- see ALEXANDRITE in the PRINCIPAL COMMERCIAL GEMSTONES SECTION. A Sri Lankan Alexandrite is shown in the GREEN GEMSTONES section of the database at GN4 Dark and brownish green
The subject I have chosen for the July entry in THROUGH MY SPECTROSCOPE is The relationship between Colour Change, Pleochroism and Absorption Spectra in Alexandrite. This is from my work on an Alexandrite crystal from Odisha (formerly Orissa) in India kindly on loan from Alan Hodgkinson.
PINK GEMSTONES - PK1 Lilac pink Gemstone # PKF0944 which was designated as SGG has been altered to TGG following recent information that after further chemical analysis it was found to contain terbium as a main constituent as opposed to samarium. This specimen is strongly magnetic.
GREEN GEMSTONES - GN2 Yellowish and greyish green A pale green diopside has been added.
GN3 Bluish green A dark bluish green tourmaline has been added.
GN4 Dark and brownish green It as been a long time in coming but now this completes my green stones section as far as I can at present. Other specimens will be added such as enstatite, but for now I will move on to the brown gemstones. This raises a question which is - at what point does a brownish green stone become a greenish brown stone? As with all the other hues throughout the optical spectrum there is no satisfactory answer to these transitions, so forgive me if this is calibrated by my own optic sensors even although they are becoming somewhat unreliable with age.
PRINCIPAL COMMERCIAL GEMSTONES SECTION. - Still working on the new page for alexandrite which should hopefully be up and running soon.
GREEN GEMSTONES - Excel file GN3 Bluish green has been added to the Green Gemstones listed in the left hand column on my Database Page. This group have a bluish overtone through pale to darker greens.
Also another two examples has been added to my Xcel file GN2 Yellowish and greyish green One is a fine heart shaped yellowish green demantiod garnet on loan courtesy of Alan Hodgkinson. The other is a synthetic spinel which shows a good manganese spectrum.
The next group in the Green Gemstone section will be the Dark and Brownish Green group. This will include alexandrite and I shall also to create a new page for this important gemstone in the PRINCIPAL COMMERCIAL GEMSTONES SECTION.
FAULTY IMAGES - This topic is discussed in this month'sTHROUGH MY SPECTROSCOPE as a guide to those who may have difficulty in observing a good clean image through a spectroscope.
GREEN GEMSTONES - The second group in the green gemstones section is now in my database. Stones in this group have either a yellowish or greyish overtone to varying degrees. A gemstone of particular interest in this group is a green chrysoberyl which struggles hard to be classified as an alexandrite but, in my opinion, can't quite make it. To view this Excel file go to GN2 Yellowish and greyish green
ORANGE GEMSTONES - Another gemstone has been added to my Excel file OR1 This is a bright orange Malaia Garnet which is one of the pyrope-spessartine series.
LASER TECHNOLOGY - The use of laser pens of known wavelength is described in THROUGH MY SPECTROSCOPEas a guide to calibration with the spectroscope.
Best wishes to all my viewers for a
HAPPY AND HEALTHY NEW YEAR IN 2012
from John Harris
GREEN GEMSTONES - At last the first group in the green gemstones section has been uploaded in my database. This group contains stones having a fairly mid tone green without too much overtone of yellow, blue or brown when viewed in un-polarised daylight. To view this Excel file go to GN1 Mid-green Three more groups in the Green section are under construction and will be uploaded in due course.
ORANGE GEMSTONES An orange coloured garnet top doublet has been added to OR1 which displays a faint almandine spectrum.
YELLOW GEMSTONES - Another CZ YLF0959 has been added to YL1 This stone shows a strong rare earth spectrum and has a colour change to green under a triphosphor lamp.
PINK GEMSTONES - Three more pink stones have been added. Grossular garnet and hydro-grossular garnet are now included in PK2 Pink and orangy pink and another CZ PKF0960 (Nd.) in PK3 Brownish and purplish pink
SPECTROPHOTOMETER CHART AND VISUAL SPECTRUM This is the topic of discussion in this month THROUGH MY SPECTROSCOPE in which I explain the correlation between the two.
YELLOW GEMSTONES - Two more species have been added to the Excel File YL1 These are Spodumene and Orthoclase. The stones and spectra were photographed from fairly large specimens kindly on loan from Alan Hodgkinson.
GREEN GEMSTONES - Work on this section of my database is underway. Due to the number of species, varieties and many hues of green this extensive group may be released in sub sections similar to the red group.
A new page on YELLOW GEMSTONES has been added to the SPECTRA DATABASE. To view this go direct to YL1. Other yellow gems will be added to this as I proceed further.
The new special blue colour filter mentioned in January is now included in the Excel file CF2 and a reference to it's use is shown on the page on DIAMOND It is also discussed in THROUGH MY SPECTROSCOPE This is the new HANNEMAN - HARRIS CAPE LINE FILTER introduced at the Tucson Gem. Show in February this year by Dr. W. Hanneman.
I have recently had the privilege to examine and photograph the spectra of an unusual zircon. This is described in this month's THROUGH MY SPECTROSCOPE and is now also included in SPECTRA OF PRINCIPAL COMMERCIAL GEMSTONE ZIRCON (High type)
The new Colour Filter referred to below made it's appearance at The Tucson Gem Show earlier this month an will be described and illustrated on this website shortly.
Look out soon for a new special filter which will be introduced to the database. This will also be discussed in THROUGH MY SPECTROSCOPE when it is released on to the market by the manufacturer.
PINK STONES A new entry has been added to PK1 This SYNTHETIC PINK FLUORITE , kindly on loan from Alan Hodgkinson, shows a good rare earth spectrum possibly due to erbium.
A new page has been added on COLOUR FILTERS which is still under construction. Only a brief introduction is given at present and this will be expanded considerably soon. The Excel files on colour filters are well underway and will be added to the Spectra Database in due course. The next section to be added to the Gemstone Spectra Comparison will be the Yellow Gemstones including a striking example of Samarium Gallium Garnet.
THROUGH MY SPECTROSCOPE This page has an interesting entry for students, and possibly the professional gemmologist, who may find difficulty locating the 415nm. line due to nitrogen in diamond.
THROUGH MY SPECTROSCOPE - This has now been given a separate page for ease of reference to previous entries and will be periodically updated as time permits.
The GEMSTONE SPECTRA COMPARISON section has been updated and now includes orange coloured stones in an additional Excel file OR1. I had intended at this stage to no longer include the column showing the spectra reading from 700nm. (Red) on the left to 400nm. (Blue) on the right but there seems to be still a lot of viewers who would prefer to have this facility so I shall continue to include this. This file has been arranged from pale orange through to darker brownish orange gemstones for comparison.
To view this file OR1 go to SPECTRA DATABASE and follow the link to ORANGE GEMSTONES.
COLOUR FILTERS - A new page on this subject will be added soon, together with another Excel file included in the spectra database showing the filters and their spectra.
Principal Gemstones; One more page has been added. This is for Green, blue and violet SPINEL. To view this page go to the SPECTRA DATABASE and follow the link.
The Excel files for Colour Filters and for Orange Gemstones are well under way for addition to the database so watch this space.