# What type of fibers or minerals do you find in the extracellular matrix of bone? How does this composition relate to the properties of bone?

Calcium-containing salts are the most important minerals to bones, making up around 70% of the matrix, including mostly calcium phosphate (hydroxyapatite, $C {a}_{5} {\left(P {O}_{4}\right)}_{3} \left(O H\right)$ ) and some amount of calcium carbonate and other calcium or phosphate salts. These provide rock-like rigidity, literally, as limestone is largely calcium carbonate. There are trace amounts of other minerals like magnesium, sodium and potassium, which lends metallic support.