Sizes will vary on the rough tumbles.
Amphiboles are a group of rock-forming chain silicates that occurs in many igneous and metamorphic rocks. Their complex structure allow to incorporate several different elements in solid solution, producing a wide chemical variability. The name itself derives from the Greek – amphibolos (double entendre, ambiguous), in reference to the chemical and morphological complexity of this group of minerals. The term was coined by the French crystallographer René-Just Haüy.