http://www.uned.es/cristamine/gemas/indice.htm
http://www.eldoradocolombia.com/las_esmeraldas.html
http://www.esmeraldacolombia.com/script/
http://es.wikipedia.org/wiki/Esmeralda
http://www.ige.org/WebRoot/acens/Shops/ige_org/MediaGallery/refractometro.swf
http://www.ige.org/epages/ige_org.sf/es_ES/?ObjectPath=/Shops/ige_org/Categories/LABS
http://www.flickr.com/photos/mariagoti/544504215/in/set-72157600264076879/
http://www.flickr.com/photos/gemstones/840852912/in/photostream/
http://www.flickr.com/photos/adamantine/203921016/in/set-72057594099887808/
http://www.flickr.com/photos/7844000@N08/1548766429/in/set-72157602275303559/
