Table 6.

Total and respirable quartz levels as measured from scanning electron microscopy (SEM).

Major coal type	County	Coal sub-type	Coal mine	N	Total Quartz (% of coal)	Respirable Quartz* (% ofcoal)
Smoky	Xuanwei	Coking		19	4.58^	1.93 ^
				11	6.77	3.1
				10	7.52	3.39
			Azhi	2	4.11	2.33
			Baoshan	1	6.4	3.83
			Laibin	2	10.48	5.69
			Tangtang	4	7.52	3.39
			Yangchang	1	11.97	1.28
	Fuyuan	Coking		8	3.24	1.14
				3	4.58	1.87
			Daping	1	3.82	0.93
			Enhong	1	7.39	2.46
			Haidan	1	4.58	1.87
		1/3 coking		2	1.87	0.98
			Bagong	1	1.08	0.63
			Dahe	1	2.66	1.33
		Gas fat	Housuo	2	16.5	9.83
		Meagre lean	Gumu	1	2	0.96
Smokeless				6	2.24	0.60
	Fuyuan		LaoChang	4	2.41	0.85
	Xuanwei		RSXZ	2	1.77	0.27

Italicized data indicate overall value for each county.

^{^}Statistically significant variation between smoky & smokeless coal types.

^*Respirable quartz represents quartz grains of size less than 9.6 μm.