Particles

Red in colour

Minerals

Birefraction

l8

+

biotite

slightly; but the birefringency is masked by sombre proper-tint of the mineral

l11

+

phosphorite clay, iron-rich

no

l14

lightly

a brick fragment

no

l15

calcite

+

l17

yellow-red

K-aluminosilicate

no

l18

a silica

no

l26

+

K-aluminosilicate

no

l34

at the top

a washing powder

no

l38

a wax

no

l39

+

hematite

no

l40

calcium carbonate

+

l41

quartz

no