Raw Magnesite Powder
Magnesite is a magnesium carbonate mineral with a chemical composition of MgCO3. It is named after the presence of magnesium in its composition. Magnesite usually forms during the alteration of magnesium-rich rocks or carbonate rocks by metamorphism or chemical weathering.
Magnesite is used to produce magnesium oxide (MgO), which serves as a refractory material for the steel industry and as a raw material for the chemical industry. Small amounts of magnesite are also used as a gem and lapidary material
Properties of Magnesite:
Magnesite can be difficult to identify in hand specimens because it often departs from its anticipated properties. It is often cryptocrystalline, which can obscure its cleavage. Magnesite is often silicified or in an admixture with chert, which makes it deceptively hard. The presence of significant chert will also reduce the apparent effervescence with HCl.
If you want to identify magnesite, the steps below will probably be helpful. Some assume that you have a specimen that can be used for destructive testing.
| Physical Properties of Magnesite | |
|---|---|
| Chemical Classification | Carbonate |
| Color | White, grayish, yellowish, brownish, rarely colorless |
| Streak | White |
| Diaphaneity | Cryptocrystalline material is usually opaque; otherwise translucent to transparent. Often impure. |
| Cleavage | Perfect, but often not seen in cryptocrystalline specimens. |
| Mohs Hardness | 3.5 to 5.0 |
| Specific Gravity | 3.0 to 3.2 |
| Diagnostic Properties | Can be hard to identify and is often confused with howlite. Effervesces in room-temperature dilute HCl (5%) when powdered. Perfect cleavage if visible. Specific gravity higher than howlite. Refractive index of 1.509 to 1.700 with strong birefringence blink. |
| Chemical Composition | MgCO3 |
| Crystal System | Trigonal |
| Uses | Heated to produce MgO which is used to produce refractory bricks, refractory cements, magnesium metal. High-quality pieces of magnesite are used to cut beads, cabochons, tumbled stones, and other lapidary projects. |