AllMineralsRock
Gypsum Vs. Quartz
Gypsum is a very popular mineral composed of calcium sulfate.[1] Quartz is also a very popular gemstone and its chemical composition is silicon dioxide.[2]
Quick Facts on Differences of Gypsum and Quartz
For a quick recap of the differences gypsum and quartz:- In terms of crystallography, gypsum is monoclinic while quartz can be hexagonal or trigonal.
- For chemical formulas, gypsum is CaSO4· 2H2O while quartz is SiO2.
- While both gypsum and quartz can be vitreous, in terms of luster, gypsum can be pearly and quartz can be greasy or waxy.
- While both gypsum and quartz can be commonly red or yellow, gypsum is often brown.
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Gypsum's hardness is lower than quartz - gypsum ranges from 1.5 to 2 and quartz is 7 on the Moh's scale.
- Gypsum can be scratched by a finger nail (2.5), copper pennies (3.5), the average knife blade (4.5), glass (5.5) or quartz (7) while quartz can not be.
- Gypsum's specific gravity is lower than quartz - gypsum ranges from 2.3 to 2.32 and quartz ranges from 2.651 to 2.91.
Quick Facts on Similarities of Gypsum and Quartz
The similarities of gypsum and quartz include:- Gypsum and quartz both can be opaque, translucent or transparent.
- Gypsum and quartz both streak white.
- Gypsum's rarity is similar to quartz.
Summary of Gypsum
Gypsum is a soft, white or gray mineral that belongs to the sulfate mineral family. It is composed of calcium sulfate dihydrate (CaSO4·2H2O) and is commonly found in sedimentary rocks. Gypsum is often found in thick beds or layers, and its crystals are usually flat and elongated. It has a hardness of 2 on the Mohs scale and a specific gravity of 2.3. One of the unique properties of gypsum is that it loses water when heated, which makes it an excellent material for making plaster.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 Gypsum vs Quartz
| Gypsum (src) | Quartz (src) | |
|---|---|---|
| Transparency | transparent, translucent, opaque | transparent, translucent, opaque |
| Chemical Formula | CaSO4· 2H2O | SiO2 |
| Chemical Composition | calcium sulfate | silicon dioxide |
| Specific Gravity | 2.3, 2.32, 2.33 | 2.651, 2.91 |
| Hardness | 1.5, 2 | 7 |
| Streak | white | white |
| Crystallography | monoclinic | hexagonal, trigonal |
| Refractive Index | 1.52, 1.53 | 1.544, 1.553 |
| Hydrous | Yes | No |
| Colors | common: brown, red, yellow sometimes: blue, green, white, orange less common: tan, gray, pink, beige, black, colorless, band |
common: red, yellow sometimes: blue, gray, pink, black, brown, green, white, orange, purple, violet, colorless, multicolor |
| Solubility | Soluble in dilute HCl | Insoluble at STP |
| Category | sulfate | silicate |
| Birefringence | δ = 0.010 | δ = +0.009 (B-G interval) |
| Fracture | uneven | conchoidal, uneven |