This is a complete remake of NewIOR.inc. It contains +2850 minerals with IOR values and usually also the birefringence values. If you have used an earlier version of this file, please go through it and update your files as needed because there are MAJOR CHANGES here!
Added 38 real dispersion values.
Changed the license from the OPEN PUBLICATION LICENSE to The GNU Lesser General Public License, v2.1, making me able to state:
This software is OSI Certified Open Source Software. OSI Certified is a certification mark of the Open Source Initiative.
The file is available here.
If you spot an error, please don't hesitate contacting me! Comments, add-ons, corrections etc. are much appreciated to:
Email : email@example.com WWW : http://www.seasoft.tecbox.com/ Snailmail : Sven-Erik Andersen : Langneshøgda 5A : N-8624 Mo I Rana : NORWAY
IMPORTANT! PLEASE READ!
Many of the mineral-names don't "translate" well into a format that POV-Ray will accept, so I have had to change some of the names. A name like Pumpellyite-(Fe+++) has been changed to Pumpellyite_FePlusPlusPlus. I have made a file listing the names and the POV-Ray version of their name. It is available here (334 kb!!!).
Birefringence is the difference between the highest and lowest IOR in a mineral. Most minerals have a very low birefringence, notable exceptions is the carbonates. The birefringence causes the ray of light that enters a mineral to split in two rays, one slow and one fast. When the two rays exits the crystal they are bent in two different angles. If you were to look through such a mineral (maybe calcite, it has one of the highest birefringence values), you would see two pictures. This is also called double refraction. I will include the birefringence values that I have, which is most of the uniaxial and biaxial minerals. Hopefully someone will create a patch so it can be of use someday.
Dispersion is a little more complex than birefringence. Birefringence is affecting all wavelengths of light equally. But refraction is affected by the wavelength too. Blue light is bent more than green light, which is bent more than red light. When the dispersion is low, the white light exits the crystal almost unaffected and we see it as white light. But if the dispersion is high, the different colours are bent in different angles. This is the effect that causes the fire or flashes of colours in cut gemstones like diamond and zircon. This is also the effect that causes the light to split in a glass prism or a drop of water, giving us the rainbow.
The IOR_Dispersion.inc file has been emptied because I had erroneously used the multiple IOR-values from the biaxial and uniaxial minerals. I hope to re-make it, but it will require some more "digging" into reference material. If you need a dispersion-value (with MegaPOV's dispersion function), then you might try to use the birefringence value for that mineral and add 1...
The crystals have been separated into 3 files based on their cleavage structure. The subject is fairly complex, and I have not figured it all out yet. So I will not have a long explanation on the subject here. If you want to read up on it, then take a look at some of the websites that I have listed above, particularly the links section of the Mineralogy Database (http://web.wt.net/~daba/Mineral/index.htm).
Isometric and amorphous (like glass) minerals have essentially the same structure or lack there of, in all directions and so have only one index of refraction and are called isotropic minerals. These minerals are listed in the IOR_Isotropic.inc file.
These minerals do not have an ordered structure like crystals. They include most types of glass, and minerals like amber, opal, tektites and obsidian. These minerals are listed in the IOR_Isotropic.inc file with the isometric minerals.
Hexagonal, trigonal and tetragonal minerals have a different structure along their primary axes than they do in all other directions and for this reason they have two indices of refraction, one along the primary axis and one for every other direction. These minerals are called uniaxial minerals for their one unique direction. These minerals are listed in the IOR_Uniaxial.inc file.
Orthorhombic, monoclinic and triclinic minerals have two planes of equal refractive indices and are called biaxial. These minerals are listed in the IOR_Biaxial.inc file.
The gemstones are also listed in a separate file called IOR_Gemstones.inc making it easier to locate the values if you are only interested in those.
Good resources on the net