AMPHIBOLE GROUP

The amphiboles found in the district are tremolite (including asbestos and actinolite), cummingtonite (zinc-bearing), edenite, hastingsite, pargasite, and crocidolite. Their relation in composition, according to the classification of Berman and Larsen (279), is as follows:

1. Alkali-free members:
			Tremolite (actinolite), Ca₂(Mg,Fe")₅Si₈O₂₂(OH)₂
			Zinc cummingtonite (Mg,Fe",Mn,Zn)₇Si₈O₂₂(OH)₂
2. Alkali-bearing members:
	a. Deficient in silicon:
				Edenite, Ca₂Na(Mg,Fe")₅AlSi₇O₂₂(OH,F)₂
				Hastingsite (gamsigradite), Ca₂Na(Mg,Fe",Mn)₄(Al,Fe''')₃Si₆O₂₂(OH)₂
				Pargasite, xCa₂Na(Mg,Fe",Mn)₄Al₃Si₆O₂₂(OH,F)₂ + yNa₃Fe"₄Fe'''Si₆O₂₂(OH,F)₂
		b. With normal amount of silicon:
				Crocidolite, Na₂Mg₃(Fe''',Al)₂Si₈O₂₂(OH)₂

Forms
a(100), b(010), m(110), t(101), p(-101), r(011), i(031), d(-111), k(-211), z(-121), and v(-231). (Dana's position.)

**Combinations on amphibole crystals**
	Forms	Varieties	Localities	Illustrations
1	b, m, r	Tremolite	Franklin
2	a, b, m, r	Tremolite	Sterling Hill
3	m, r	Edenite	Franklin	Figure 93
4	b, m, r, v ,z	Edenite	Fowler quarry	Figure 94
5	b, m, p, r, i, z	Edenite	Fowler quarry	Figure 95
6	b, m, p, r, v, z	Edenite	Sterling Hill	Figure 96
7	a, b, m, t, p, r, i, k, v, z	Edenite	Sterling Hill	Figure 97
8	b, m, p, r, i, k, v, z	Edenite	Sterling Hill	Figure 98
9	b, m, t, r, i, k, v. Twin	Edenite	Sterling Hill	Figure 99
10	b, m, t, p, r, i, k, v, z. Twin	Edenite	Franklin	Figure 100
11	b, m, p, r, i	Edenite	Franklin	Figure 101
12	b, m, p, r, i, k, v, z	Hastingsite	Sterling Hill	Figure 102
13	b, m, p, k	Hastingsite	Sterling Hill
14	b, m, p, r, z	Hastingsite	Sterling Hill
15	b, m, p, r, k	Hastingsite	Sterling Hill
16	b, m, p, r, i, k, z	Hastingsite	Sterling Hill


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	This page created: January 12, 2001 5:39 PM