Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos
mineral
References & Edit History Related Topics
Images & Videos
A vivid blue, textured mineral specimen of azurite displayed against a pale purple background. Trigonal system A schematic diagram shows the cubic crystal structure of pyrite, FeS2, with blue spheres representing ferrous iron cations (Fe2+) and yellow spheres representing sulfur anions (S-) arranged in a three-dimensional grid. franklinite, willemite, and calcite A cluster of pyrite crystals with a metallic gold appearance is shown, featuring both pentagonal dodecahedron shapes and striated cubic forms. Insets highlight the detailed structure of a pentagonal dodecahedron and a striated pyrite cube, with labels explaining their geometric outlines and the mineral's composition of iron and sulfur ions. azurite Cueva de los Cristales Diagram showing four types of translation-free symmetry in crystals: a sixfold axis of rotation, a fourfold axis of inversion, a center of symmetry, and a mirror plane, each illustrated with a labeled purple crystal shape and explanatory text. Three illustrated crystals are shown to demonstrate different crystal classes and symmetries: a tall, prismatic monoclinic gypsum crystal; a pointed, double-ended tetragonal wulfenite crystal; and a cubic isometric halite crystal, each labeled with its crystal class and symmetry content.
What Are the Seven Basic Crystal Systems?
At a Glance
A clear, faceted quartz crystal with sharp edges and a pointed tip is displayed against a dark blue fabric background.
mineral summary
Quizzes
Basalt sample returned by Apollo 15, from near a long sinous lunar valley called Hadley Rille. Measured at 3.3 years old.
(Bed) Rocks and (Flint) Stones
ore. iron ore minerals, rock, metal, metallic iron
Rocks, Minerals, and More Quiz
Related Questions
Britannica AI Icon
Adding us as a Preferred Source tells Google you trust our content, so our articles show up more often in your Google Search, Discover feed, and AI Overviews.
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
print Print
Please select which sections you would like to print:
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites
Britannica Websites
Articles from Britannica Encyclopedias for elementary and high school students.
Written by
Cornelis Klein
Professor of Earth and Planetary Sciences, University of New Mexico, Albuquerque. Author of Minerals and Rocks; coauthor of Manual of Mineralogy.
Cornelis Klein
Fact-checked by
Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
Britannica Editors
Last updated
β€’History

Although this mineral class is large (with almost 700 known species), most of its members are quite rare. Apatite [Ca5(PO4)3(F, Cl, OH)], however, is one of the most important and abundant phosphates. The members of this group are characterized by tetrahedral anionic (PO4)3– complexes, which are analogous to the (SO4)2– groups of the sulfates. The phosphorus ion, with a valence of positive five, is only slightly larger than the sulfur ion, which carries a positive six charge. Arsenates and vanadates are similar to phosphates.

Common phosphates
apatite group
apatite Ca5(PO4)3(F, Cl, OH)
pyromorphite Pb5(PO4)3Cl
amblygonite (Li, Na)AlPO4(F, OH)
wavellite Al3(PO4)2(OH, F)3 Β· 5H2O
turquoise CuAl6(PO4)4(OH)8 Β· 4H2O
autunite Ca(UO2)2(PO4)2 Β· 10βˆ’12H2O
Source: Modified from C. Klein and C.S. Hurlbut, Jr.,
Manual of Mineralogy, copyright Β© 1985 John Wiley
and Sons, Inc., reprinted with permission of John Wiley
and Sons.