Possible Clues:

• Element in chalk, milk
• Substance periodically found at 20
• Greyish-white chemical element in bones and teeth
• The element is without wind about a hundred and one and you
• Bone-building element
• White metallic element in limestone, chalk
• Element present in limestone, chalk and gypsum
• With 91-Down, hypertension control option
• Constituent of bones
• Mineral in milk