Editing Onyx (material)

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{{SeeWikipedia|Onyx}}
<center>''Looking for [[Onyx]], the planet?''</center>
[[Image:Black_Onyx.jpg|thumb|right|150px|Six pieces of onyx]]
'''Onyx''' is a cryptocrystalline form of quartz. Its bands of color range from white to almost any color (some with some shades of another color like purple or blue); common colors include white, tan, and brown. Pure black onyx is common, but not as common as the banded variety.

The planet [[Onyx]] had such plentiful deposits of onyx that it was named for the mineral. [[Zone 67]] on Onyx was also home to a [[Forerunner]] city built primarily of onyx.<ref>'''Halo: Ghosts of Onyx''', ''page 269''</ref> The [[Covenant Empire|Covenant]] also use onyx as a decorative material.<ref>'''Halo: Contact Harvest''', ''page 143''</ref>

==Description==
Onyx is usually cut as a cabochon, or into beads, and is also used for intaglios and cameos, where the bands make the image contrast with the ground. Some onyx is natural but the staining of agate produces much.

The name has sometimes been used, incorrectly, to label other banded lapidary materials, such as banded calcite found in Mexico, [[Pakistan]], and other places, and often carved, polished and sold. This material is much softer than true onyx, and much more readily available. The majority of carved items sold as 'Onyx' today are this carbonate material.

{| class="wikitable"
|+'''Technical details'''
|-
| Chemical composition and name
| SiO<SUB>2</SUB> - Silicon dioxide
|-
| Hardness (Mohs scale of mineral hardness)|Mohs scale)
| 7
|-
| Specific gravity
| 2.65 - 2.667
|-
| Refractive index (R.I.)
| 1.543 - 1.552 to 1.545 - 1.554
|-
| Birefringence
| 0.009
|-
| Optic sign
| Positive
|-
| Optical character
| Uniaxial
|}<br />

==List of appearances==
*''[[Halo: Ghosts of Onyx]]'' {{1st}}
*''[[Halo: Contact Harvest]]'' 

==Sources==
<references/>
[[Category:Materials]]
[[Category:Geology]]