AllMineralsRock
Opal Vs. Quartz
Opal is a very popular gemstone composed of silicon dioxide.[1] Quartz is also a very popular gemstone and its chemical composition is also silicon dioxide.[2]
Quick Facts on Differences of Opal and Quartz
For a quick recap of the differences opal and quartz:- While both opal and quartz can be translucent or transparent, quartz can be opaque.
- For chemical formulas, opal is SiO2· nH2O while quartz is SiO2.
- While both opal and quartz can be vitreous or waxy, in terms of luster, opal can be pearly and quartz can be greasy.
- While both opal and quartz can be commonly red, quartz is often yellow.
- Opal's specific gravity is lower than quartz - opal ranges from 1.98 to 2.25 and quartz ranges from 2.651 to 2.91.
Quick Facts on Similarities of Opal and Quartz
The similarities of opal and quartz include:- Opal and quartz both streak white.
- Opal's rarity is similar to quartz.
Summary of Opal
Opal is a mineraloid that is formed from the silica-rich water that permeates through the earth's crust. It is a beautiful gemstone that is known for its unique play of colors. Opal is a non-crystalline mineral that is made up of tiny spheres of silica, which diffract light in a way that creates a rainbow of colors. The colors of opal can range from white, gray, and black to red, orange, yellow, green, blue, and purple.Summary of Quartz
Quartz is a mineral that is composed of silicon and oxygen atoms arranged in a continuous framework of SiO4 silicon-oxygen tetrahedra. It is one of the most abundant minerals found in the Earth's crust. Quartz can be found in a variety of colors such as white, pink, purple, brown, gray, and black. It is also known for its unique crystal structure, which is hexagonal in shape, and its hardness, which is 7 on the Mohs scale.Table Comparison of Opal vs Quartz
| Opal (src) | Quartz (src) | |
|---|---|---|
| Transparency | transparent, translucent | transparent, translucent, opaque |
| Chemical Formula | SiO2· nH2O | SiO2 |
| Chemical Composition | silicon dioxide | silicon dioxide |
| Specific Gravity | 1.98, 2.25 | 2.651, 2.91 |
| Streak | white | white |
| Hydrous | Yes | No |
| Colors | common: red sometimes: blue, gray, pink, black, brown, green, white, orange, purple, yellow, colorless, band, multicolor |
common: red, yellow sometimes: blue, gray, pink, black, brown, green, white, orange, purple, violet, colorless, multicolor |
| Solubility | Soluble in hot salt water, bases, HF | Insoluble at STP |
| Birefringence | none | δ = +0.009 (B-G interval) |
| Fracture | conchoidal | conchoidal, uneven |