Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography

A quiz about a mineral optic figure: just experimenting with the code

Last Updated: 22nd Mar 2020

By Frank K. Mazdab

After watching this short (30 sec) video of an optic figure, please answer the accompanying questions:

1. What is the optical nature of this mineral?

2. Based on the optical nature of this mineral, select all of the possible crystal systems that could be consistent with this figure?

3. Based on the figure, what is the optic sign of this mineral? Assume the microscope uses a standard accessory plate orientation, with the "slow" ray vibration direction of the accessory plate oriented NE-SW.

4. Assuming the entire diameter of the circular field of view represents a 2V° angle of 60°, approximately what 2V° angle is shown by the mineral in this figure?

5. Based on the figure, which answer best describes the observed dispersion of this mineral?

6. Based on your answers to the preceding questions, and using the mindat database to look up optical properties (check the links provided), which one of the following minerals is most likely represented by this optic figure?

Article has been viewed at least 196 times.

Discuss this Article

22nd Mar 2020 09:40 GMTJolyon Ralph Founder

Thank you!

I fixed the formatting, the problem was trailing spaces after the </answer> tags

22nd Mar 2020 09:49 GMTFrank K. Mazdab Manager

thanks Jolyon!

yeah, I saw the large blank spaces after the questions but couldn't figure out where they were coming from (I copied your code from your earlier sample rather than hand-typing everything anew... it must have been in the copy/paste where I picked up the extra spaces). Appreciate you fixing that for me!  I'll keep an eye out for that in the future.
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2020, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: April 9, 2020 02:42:42
Go to top of page