Blog on gemmology
http://studiopjj.blogspot.com/2007/07/gemmology-on-shoestring_07.html
Look through their articles, a great archive of articles
http://www.professionaljeweler.com/
https://www.jewelinfo4u.com/category/gemstones/page/2
Important
http://www.agta.org/gemstones/agta-gim/index.html
http://www.rockhounds.com/rockshop/table.shtml
http://www.feeg.net/
http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/index-back-issues-1934-80.html
http://www.gia.edu/research-resources/gems-gemology/gemsgemologycurrentissue.html
http://www.galleries.com/minerals/physical.htm
http://www.preciousgemstones.com/Forecasters.html
http://dendritics.com/scales/gem-links.asp

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Charts and Tables
http://nature.berkeley.edu/classes/eps2//wisc/tables.html
https://www.gemsociety.org/gemstone-encyclopedia/
http://www.gemlabtools.com/ri-alphabetical.html
http://www.gemlabtools.com/gems-news--advice.html
http://gemologyonline.com/gemstone.html
http://www.gemselect.com/gem-info/refractive-index.php
http://www.gemselect.com/gem-info/dispersion-chart.php
http://ayurvedicjewelry.com/planetary_gems.html
http://www.gemselect.com/gem-info/specific-gravity.html
http://www.prettyrock.com/php/mineral-properties.php?single_property=specific_gravity
http://www.gemselect.com/gem-info/cleavage-chart.php
http://www.csgnetwork.com/gemchar.html
http://gemologyonline.com/csi.html
http://www.yourgemologist.com/ChartsandGraphs/ChartsandGraphs.html
http://www.gci-gem.com/gtables.html#
http://www.csgnetwork.com/gemologicalconverters.html
https://www.gemsociety.org/article/table-refractive-index-double-refraction-gems/
http://www.gemstones-guide.com/Table-of-Hardness-S.G.-R.I.-of-Gemstones.htmlhttp://www.gemhut.com/metric.htm
https://www.gemsociety.org/article/standard-gem-sizes-chart/

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Gem Descriptions
http://www.yourgemologist.com/thegemstones.html
http://www.gia.edu/gem-encyclopedia
http://nature.berkeley.edu/classes/eps2//wisc/image.html
http://nature.berkeley.edu/classes/eps2//wisc/glossary2.html
http://gemologyproject.com/wiki/index.php?title=Alphabetic_list_by_gemstone_name0--"
http://gemologyonline.com/gemstone.html
http://www.cigem.ca/510.html
http://www.agta.org/gemstones/index.html
https://www.gemsociety.org/gemstone-encyclopedia/
http://www.gemlabtools.com/gem-photo-library.html
http://www.gehnabazaar.com/gemstones/34/coral.html (Look at the gem listings on the right of this page)
http://www.gemhut.com/info.htm
http://www.edelsteine.at/gemstone-glossary/a/
http://www.palmbeachgems.com/gemstone_articles.htm
http://www.galleries.com/minerals/physical.htm
http://www.galleries.com/minerals/byname.htm
http://www.yourgemologist.com/zandrite.html
http://www.handmadebeadedjewelry.org/blog/gemstone-list-info/#ac
http://www.awesomegems.com/gemfacts.html
http://www.alexandrite.net/chapters/
http://www.bwsmigel.info/A-Z.ppt.pdf
http://www.gemtec.com/
http://www.nordskip.com/mawsitsit.html
http://www.apsara.co.uk/index.php
http://www.gia.edu/gems-gemology/summer-2015-rubies-sapphires-snezhnoe-tajikistan
http://gemologyproject.com/wiki/index.php?title=Ruby
Exerpts from Richard Hughes great book on rubies and saphires
http://www.ruby-sapphire.com/r-s-bk-quality3.htm
http://www.ruby-sapphire.com/r-s-bk-quality4.htm

Minerals
Wurzburg Museum mineral specimens
http://www.equisetites.de/gallery/index.htm
http://www.gimizu.de/sgmcol/
http://homepages.udayton.edu/~koziolam/resminpet.html
http://webmineral.com/
http://webmineral.com/crystall.shtml#.Vd_i0KjYbSA
http://www.mindat.org/index.php
http://www.gly.bris.ac.uk/www/teach/opmin/mins.html
http://earthsci.org (Earth Science Australia told us of a number of these mineral sites)
http://www.galleries.com/Minerals
http://earthsci.org/mineral/rockmin/mineral/mineral_optics/min_opt.html http://www.lapigems.com/Articles/Tanzanite-Crystallography.aspx

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Gemstone Inclusions
http://www.cigem.ca/inclusion/inclusions.html
https://www.cigem.ca/inclusion/ru01.html
http://www.ruby-sapphire.com/r-s-bk-ch5.htm
http://www.apsara.co.uk/index.php/gallery/inclusions/inclusion-gallery.html
http://www.gemyes.com/gemology.html
http://microworldofgems.com/photomicrography.php (download article at bottom of this page)
http://www.palagems.com/inclusions.htm
http://www.flickr.com/groups/1158167@N23/
http://www.hkdlab.ca/gemstoneinclusion.htm
http://www.edelsteine.at/gemstone-treatments/
http://www.bwsmigel.info/Lesson5/DE.Magnification.html
http://www.flickr.com/search/?q=%22gemstone+inclusions%22&w=all&s=int&referer_searched=1
http://www.microworldofgems.com/pdf/Koivula_Sp03.pdf
http://www.gia.edu/gem-inclusion-insight
http://www.gemresearch.ch/inclusions/
https://www.youtube.com/watch?v=aDoTEFat5JY
http://www.sciencealert.com/gallery-gems-under-the-microscope-reveal-the-beauty-of-imperfections
http://anthonydegoutiere.com/photo-gallery/
http://www.lapigems.com/Articles/Tsavorite-Inclusions.aspx
http://www.lotusgemology.com/library/articles/324-hyperion-sources-literature-on-inclusions-in-gemstones
http://www.kashmirblue.com/Research/inclusions.html
http://www.gia.edu/gem-inclusion-insight
https://www.gemsociety.org/article/inclusions/
http://www.ruby-sapphire.com/r-s-bk-ch5.htm
http://www.microworldofgems.com/pdf/Koivula_Sp03.pdf

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Visual Optics (Hanneman-Hodgkinson Slit Technique)
http://www.cigem.ca/411.html
http://www.cigem.ca/421.html
http://www.scotgem.co.uk/moissonite.htm (really good info on moissanite)
http://www.pricescope.com/forum/faq1/visual-optics-special-weapons-tactics-for-guerilla-gemology-t10635.html
http://accreditedgemologists.org/pastevents/2011abstracts/Hodgkinson.php
http://facetingacademy.com/learn-faceting/learn-faceting-free/gem-identification/
http://www.pricescope.com/idealbb/view.asp?topicID=10635
https://www.youtube.com/watch?v=oi0YTNYGCqk
Equipment  and gemmology articles
http://www.internetstones.com/introduction-to-tools-instruments-gemology-mineralogy-diamond.html
http://www.jewelinfo4u.com/Gemstone_Testing_tools.aspx
http://www.gemsociety.org/info/agem5.htm
http://nature.berkeley.edu/classes/eps2//wisc/Lect5.html
http://www.emporia.edu/earthsci/amber/go340/gemtest.htm
https://www.gemsociety.org/gemology/gemology-tools/
http://www.yourgemologist.com/studyofgemology.html

Polariscopes
http://www.yourgemologist.com/Polariscope/polariscope.html (check out the rest of the articles here)
http://www.yourgemologist.com/Sunglass%20Polariscope/sunpolariscope.html
http://www.ganoksin.com/borisat/nenam/polaris.htm
http://gemologyproject.com/wiki/index.php?title=Polariscope
http://www.free-form.ch/storys.html (check out the rest of this site)
http://gemologyproject.com/wiki/index.php?title=Equipment_used_to_identify_gemstones
http://homepage.rub.de/olaf.medenbach/eng.html (amazing images of interference figures-advanced stuff)
Fantastic spectra database
http://www.jewelinfo4u.com/Spectroscope.aspx
http://www.gemlab.co.uk/SpectraDatabase.html
http://www.prettyrock.com/spectroscope-instructions.htm
http://www.lotusgemology.com/index.php/library/articles/282-the-hand-spectroscope-for-testing-ruby-sapphire
https://www.google.ca/?gfe_rd=cr&ei=wshEWKvAB4Wj-AONtoG4BQ#q=spectroscope+gemology
Chelsea filter reactions
http://gemologyonline.com/chelsea_filter.html
http://www.free-form.ch/tools/chelsea.html
Refractometer
http://www.stonegrouplabs.com/bright_linetechnique.pdf
https://www.youtube.com/watch?v=DEC-JxsA7WY
http://gemologyproject.com/wiki/index.php?title=Refractometer
http://prettyrock.com/refractometer-instructions.htm
http://www.yourgemologist.com/Refractometer/refractometer.html
Immersion facet contrast used with new sapphires
http://www.ruby-sapphire.com/treated_orange_sapphire.htm

Fluorescence
http://www.ruby-sapphire.com/heat_seeker_uv_fluorescence.htm

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Diamonds, their simulants and synthetic diamonds
http://www.gemsociety.org/info/chsize.htm
http://nature.berkeley.edu/classes/eps2//wisc/Lect6.html
http://www.attawaygems.com/NMFG/update_on_synthetic_diamonds.html
http://dendritics.com/scales/synthetic-diamonds-final-report.asp
http://www.professiona ljeweler.com/archives/articles/2000/sep00/0900dg1.html
http://www.jewelryexpert.com/articles/articles.htm
http://www.gemologyonline.com/diamond_dictionary.html
http://diamondcut.gia.edu/pdf/booklet_cut_estimation_tables_highres.pdf
http://www.gia.edu/gems-gemology/summer-2013-shigley-optical-defects-diamond
http://www.igiworldwide.com/ch/pdf/DIB.pdf
http://www.diamonds.net/news/articles.aspx
http://beyond4cs.com/grading/depth-and-table-values/
http://www.a1-diamond.com/
http://beyond4cs.com/grading/clarity-characteristics/types-of-inclusions/
http://www.lumeradiamonds.com/diamond-education/diamond-clarity
http://yourdiamondteacher.com/diamond-4cs/clarity/diamond-inclusions-types-list/
http://4csblog.gia.edu/2013/diamond-inclusions-defined
https://www.youtube.com/watch?v=Xein8mAOjNg
http://www.jckonline.com/2016/02/19/everything-you-need-know-about-synthetic-and-simulant-diamonds
http://www.ajediam.com/Fake_or_Real_Diamonds_Test_detect_difference.html
http://www.gemologyproject.com/wiki/index.php?title=Diamond
Great article on diamond simulant detection by Hodgkinson
http://www.scotgem.co.uk/moissonite.htm
Separating Diamond simulants
http://www.nordskip.com/notes
Moissonite notes
http://www.scotgem.co.uk/moissonite.htm
http://www.realorrepro.com/article/Moissanite:-diamond-imitation
http://ocgold.com/blog/?p=12010
http://www.moissaniteco.com/pdf/Synthetic-Moissanite-A-New-Diamond-Substitute.pdf
http://beyond4cs.com/faq/how-to-spot-a-fake-diamond/identify-a-moissanite/
Cubic zirconia id
http://www.yourgemologist.com/CubicZirconia/cubiczirconia.html
http://www.wikihow.com/Tell-if-a-Diamond-is-Real
http://www.abazias.com/diamondblog/diamond-education/tests-to-tell-genuine-diamond-from-cubic-zirconia
http://www.abazias.com/diamondblog/diamond-education/how-to-tell-the-difference-between-a-real-diamond-and-a-cubic-zirconia
https://www.youtube.com/watch?v=Q76UD3hkPHs
https://www.jewelrynotes.com/differences-between-cubic-zirconia-and-diamond/

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Gem enhancements and Treatments
http://www.agta.org/gemstones/index.html
http://www.agta.org/gemstones/agta-gim/index.html
Gem enhancement manual http://www.cigem.ca/368.html
http://nature.berkeley.edu/classes/eps2//wisc/Lect10.html
http://www.multicolour.com/catalogue/columns/column122000.html
http://www.palagems.com/enhancements.htm
http://www.emporia.edu/earthsci/amber/go340/create.htm
http://gemologyonline.com/treatment.html
http://www.agta.org/education/index.html
http://www.professionaljeweler.com/archives/articles/2002/oct02/1002dg2.html
http://www.minedirect.com/GemstoneEnhancement.html
http://www.gemhut.com/enhance.htm
http://www.bwsmigel.info/Lesson8/DE.Gem.Enhancement.html
http://www.gemselect.com/gem-info/fracture-filled.php
http://www.gemselect.com/gem-info/heat-treatment.php
http://www.gemselect.com/gem-info/irradiation.php
http://www.lapigems.com/Articles/Gemstone-Treatments-Heating-and-Irradiation.aspx http://www.lapigems.com/Articles/Gemstone-Treatments-Coating-Chemical.aspxhttp://www.lapigems.com/blog/post/2013/01/17/Tanzanite-Heating-The-Facts.aspx 
http://www.yourgemologist.com/labcreatedandtreatedgemstones.html
http://www.agta.org/education/docs/brochureirradiatedgemstones/index.html

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Synthetics and Simulants
http://www.bellaonline.com/articles/art44877.asp
http://www.yourgemologist.com/synthetics.html
http://www.bwsmigel.info/Lesson9/DE.Synthetics.Simulants.html
http://gemologyonline.com/synthetics.html
http://www.bwsmigel.info/GEOL.115.ESSAYS/Synthetics.Simulants.Fakes.html
http://www.ramaura.com/
http://www.jewelinfo4u.com/How_to_differentiate_synthetic_and_natural_emerald.aspx
https://www.gia.edu/gem-imitation
http://www.gia.edu/gg-general-search?q=Simulants&subject=Techniques
http://beyond4cs.com/faq/how-to-spot-a-fake-diamond/
http://www.qcc.cuny.edu/BiologicalSciences/Faculty/rscal/gems/synth.html
Jill Hobbs great article on diamond simulants
A Simple Approach to Detecting Diamond Simulants - GIA

Synthetic Quartz
http://www.gemselect.com/other-info/detecting-synthetic-quartz.phpepubl.ltu.se/1404-5494/2008/021/LTU-HIP-EX-08021-SE.pdf
http://epubl.ltu.se/1404-5494/2008/021/LTU-HIP-EX-08021-SE.pdf
http://www.ajsgem.com/articles/citrine-quartz-crystal.html
http://www.jckonline.com/2016/01/20/buying-amethyst-today