AllMineralsRock
Orthoclase Vs. Plagioclase
Orthoclase is a popular gemstone composed of potassium aluminum silicate.[1] Plagioclase is a very popular mineral series and its chemical composition is sodium calcium aluminum silicate.[2]
Quick Facts on Differences of Orthoclase and Plagioclase
For a quick recap of the differences orthoclase and plagioclase:- While both orthoclase and plagioclase can be translucent or transparent, orthoclase can be opaque.
- In terms of crystallography, orthoclase is monoclinic while plagioclase is triclinic.
- For chemical formulas, orthoclase is KAlSi3O8 while plagioclase can be (Na, Ca)Al1-2Si3-2O8Variations in the amount of sodium and calcium; and aluminum and silicon or form different minerals in thisseries:Amountof sodium and calciumPercentage of Albite (Ab)and Anorthite (An).
- Orthoclase can be commonly green or yellow while plagioclase can be commonly blue or white.
Quick Facts on Similarities of Orthoclase and Plagioclase
The similarities of orthoclase and plagioclase include:- In terms of luster, orthoclase and plagioclase both can be pearly or vitreous.
- Orthoclase and plagioclase both streak white.
- Orthoclase's rarity is similar to plagioclase.
- Orthoclase's hardness is similar to plagioclase - they both range from 6 to 6.5 on the Moh's scale.
- Orthoclase's specific gravity overlaps with plagioclase - orthoclase ranges from 2.55 to 2.63 and plagioclase ranges from 2.6 to 2.8.
Summary of Orthoclase
Orthoclase is a mineral that belongs to the feldspar group and is commonly found in igneous rocks. It is also known as potassium feldspar and has a chemical composition of KAlSi3O8. Orthoclase can be identified by its characteristic cleavage, which forms at right angles to each other, and its pink, white, or yellow color. It has a Mohs hardness of 6-6.5, making it a relatively hard mineral.Summary of Plagioclase
Plagioclase is a type of mineral that is commonly found in igneous rocks. It is a group of feldspar minerals that are characterized by their white to gray color and striated appearance. Plagioclase is often found in rocks such as basalt, gabbro, andesite, and granite. It is also commonly found in lunar rocks.Table Comparison of Orthoclase vs Plagioclase
| Orthoclase (src) | Plagioclase (src) | |
|---|---|---|
| Transparency | transparent, translucent, opaque | transparent, translucent |
| Chemical Formula | KAlSi3O8 | (Na,Ca)Al1-2Si3-2O8Variations in the amount of sodium and calcium; and aluminum and silicon, form different minerals in thisseries:Amountof sodium and calciumPercentage of Albite (Ab)and Anorthite (An) |
| Chemical Composition | potassium aluminum silicate | sodium calcium aluminum silicate |
| Specific Gravity | 2.55, 2.63 | 2.6, 2.8 |
| Hardness | 6, 6.5 | 6, 6.5 |
| Streak | white | white |
| Crystallography | monoclinic | triclinic |
| Hydrous | No | No |
| Colors | common: green, yellow sometimes: gray, pink, black, brown, white, orange, colorless |
common: blue, white sometimes: red, gray, pink, black, brown, cream, green, orange, yellow, colorless |
| Category | silicate | feldspar |
| Fracture | splintery, uneven | conchoidal, uneven |