feldspar definition by Wordo

Noun

Any

of

a

large

group

of

rock-forming

minerals

that

,

together

,

make

up

about

60

%

of

the

earth

'

s

outer

crust

.

The

feldspars

are

all

aluminum

silicates

of

the

alkali

metals

sodium

,

potassium

,

calcium

and

barium

.

Feldspars

are

the

principal

constituents

of

igneous

and

plutonic

rocks

.