Physical features
1. Color- Variable.
2. Streak- None.
3. Luster- Waxy.
4. Cleavage- None.
5. Transparency- Translucent to transparent.
6. Fracture- Conchoidal with sharp edges.
7. Hardness- 7.
8. Forms- Cryptocrystalline silica filling geodes.
Agate is a very common silica rich mineral, that is of a microcrystalline variety of quartz, also known as chalcedony. Agate is well known for it's brightly color banding. The bands are created by traces of iron and manganese. Agate formations occur when there is water containing alkali and silica. Iron hydroxide attacks the surrounding magma (lava) which then loses water and begins to crystallize. Many agates can also be hollow, since deposition has not proceeded enough to fill the cavity. When this happens it's known as a geode. Agate are found among volcanic rocks and ancient lavas, and in cavities as a secondary mineral, often found in metamorphic surroundings like granite intrusions, also can be in some sediments worldwide.
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