page_title: Beryl
section_title: Crystal habit and structure
hierarchical_section_title: Beryl / Crystal habit and structure
caption_attribution_description: English: Beryl Crystal Structure with view down C axis showing silicate ring channels
context_page_description: Beryl is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be₃Al₂Si₆O₁₈. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, and red. Beryl can also be black in color. It is an ore source of beryllium.
context_section_description: Beryl belongs to the hexagonal crystal system. Normally Beryl forms hexagonal columns but can also occur in massive habits. As a cyclosilicate beryl incorporates rings of silicate tetrahedra of Si
  ₆O
  ₁₈ that are arranged in columns along the C axis and as parallel layers perpendicular to the C axis, forming channels along the C axis. These channels permit a variety of ions, neutral atoms, and molecules to be incorporated into the crystal thus disrupting the overall charge of the crystal permitting further substitutions in Aluminium, Silicon, and Beryllium sites in the crystal structure. These impurities give rise to the variety of colors of beryl that can be found. Increasing alkali content within the silicate ring channels causes increases to the refractive indices and birefringence.
caption: Beryl crystal structure with view down C axis
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