The material was first collected on filter paper by drone airplanes flying through the radioactive-explosion clouds; later, einsteinium and element 100 (fermium) were positively identified in coral gathered from Enewetak Atoll. Einsteinium metal has not yet been prepared.

All einsteinium isotopes are radioactive. Mixtures of the isotopes einsteinium-253 (20.5-day half-life), einsteinium-254 (276-day half-life), and einsteinium-255 (38.3-day half-life) can be produced by intensive slow-neutron irradiation of elements of lower atomic number, such as plutonium. Tracer studies indicate that the +3 oxidation state exists in aqueous solution, presumably as the Es³⁺ ion; there is also some evidence for a +2 state. Einsteinium has chemical properties very similar to those of the other actinoid elements in the tripositive state. Einsteinium-255 and einsteinium-256 eject electrons (beta particles) to form isotopes of fermium (atomic number 100), and einsteinium-253 was used to produce mendelevium (atomic number 101).