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Strontium is a soft metal like lead and, when freshly cut, has a silvery lustre.It rapidly reacts in air to take on a yellowish colour; therefore, it must be protected from oxygen for storage. Although it is widely distributed with calcium, there are only two principal ores of strontium alone, celestine (Sr SO).The same “bone-seeking” property that makes strontium-90 dangerous is beneficially employed in strontium supplements to increase bone density and growth. The metal is an active reducing agent and readily reacts with halogens, oxygen, and sulfur to yield halides, oxide, and sulfide.
About 16 synthetic radioactive isotopes have been produced by nuclear reactions, of which the longest-lived is strontium-90 (28.9-year half-life).
Strontium-89 is employed in the treatment of bone cancer, as it targets bone tissues, delivers its beta radiation, and then decays in a few months’ time (half-life 51 days).
Strontium is not an essential element for higher life-forms, and its salts are generally nontoxic.
The metal is malleable and ductile and a good conductor of electricity, but there are relatively few uses for elemental strontium.
One of them is as an alloying agent for aluminum or magnesium in cast engine blocks and wheels; the strontium improves the machinability and creep resistance of the metal.
The best evidence is contained in the Earth’s incomplete and complex but accurate stratigraphic record — a record that has been the subject of nearly two centuries of study.