Coal also contains inorganic components, known as ash. Ash includes minerals such as pyrite [24] and marcasite [25] formed from metals that accumulated in the living tissues of the ancient plants. Quartz [26], clay, and other minerals are also added to coal deposits by wind and groundwater [27]. Ash [28] lowers the fixed carbon content of coal, decreasing its heating value.

NOTES TO THE TEXT

[1] sedimentary rock��������

[2] tropical swamps���ȴ�����

[3] Lush vegetation��ïʢ��ֲ��

[4] club mosses��ʯ��

[5] horsetails����β��ľ������һ��ֲ�

[6] layers of mud and sand����ɰ��

[7] decayed plant material�����õ�ֲ�����

[8] peat����̿

[9] minerals������

[10] lignite����ú

[11] subbituminous coal������ú

[12] bituminous coal����ú

[13] anthracite������ú

[14] Permian��������

[15] Triassic��������

[16] Jurassic��٪�޼�

[17] Cretaceous�����Ѽ�

[18] Tertiary��������

[19] cellulose������

[20] reinforcing material���ӹ̵IJ���

[21] cell walls��ϸ����

[22] lignin��ľ��

[23] tannins������������

[24] pyrite��������

[25] marcasite ��������

[26] quartz��ʯӢ

[27] groundwater������ˮ

[28] ash���ҷ�

��һҳ[1][2]