Glauconite
Chemical compound
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Glauconite is an iron potassium phyllosilicate mineral of characteristic green color which is very friable and has very low weathering resistance.
It crystallizes with a monoclinic geometry. Wikipedia
Color: Blue green, green, yellow green
Classification: Mineral
Specific gravity: 2.4–2.95
Cleavage: Perfect
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: Elastic platy/micaceous, or as rounded pellets/aggregates
Crystal system: Monoclinic