Hematite Vs. Onyx

Hematite is a very popular mineral composed of iron oxide.^[1] Onyx is also a very popular gemstone and its chemical composition is silicon dioxide.^[2]

Quick Facts on Differences of Hematite and Onyx

For a quick recap of the differences hematite and onyx:

• While both hematite and onyx is opaque, onyx can be translucent.
• For chemical formulas, hematite is Fe2O3 while onyx is SiO2.
• In terms of luster, hematite can be dull or metallic while onyx can be vitreous or waxy.
• Hematite streaks brown, red, red reddish, reddish or reddish brown while onyx streaks white.
• Hematite can be commonly brown, gray or red while onyx is often black.
• Hematite's hardness is lower than onyx - hematite ranges from 5 to 6.5 and onyx is 7 on the Moh's scale.
  • Hematite can be scratched by quartz (7) while onyx can not be.
• Hematite's specific gravity is higher than onyx - hematite ranges from 4.95 to 5.26 and onyx is 2.651.

Quick Facts on Similarities of Hematite and Onyx

The similarities of hematite and onyx include:

• In terms of crystallography, hematite and onyx both can be hexagonal or trigonal.
• Hematite's rarity is similar to onyx.

Summary of Hematite

Hematite is a mineral that is commonly found in the Earth's crust. It is a form of iron oxide, and it is known for its metallic luster and reddish-brown color. Hematite is often used in jewelry and other decorative items due to its unique appearance. It is also used in the production of iron and steel, as well as in pigments and coatings.

Summary of Onyx

Onyx is a mineral that belongs to the chalcedony family, which is a type of quartz that is formed by the deposition of silica in the cavities of rocks. It is a cryptocrystalline mineral, which means that its crystals are too small to be seen with the naked eye. Onyx is typically black, but it can also be found in other colors such as white, gray, brown, and green. It has a waxy luster and a smooth, polished surface.

Table Comparison of Hematite vs Onyx