What is the rarest mineral/element/thing on the planet

And how much is there? Thanks.

Radioactive elements may be found in minute amounts because they are unstable, and so decay. Technicium, Francium, Astatine, Plutonium may all be found in very small amounts because they are radioactive.

If you only consider stable elements then Iridum, Rhodium, and Osmium are the rarest elements. All at about 1 part per billion of the crust.

They are all precious metals, and they don't react with oxygen. They are rare because they tend to sink down through the mantle into the earth's core.

Minerals are harder to determine - whereas there are a limited number of elements the number of minerals is almost boundless. However Painite is a contender for an extremely rare mineral, or Hapkeite (a mineral derived from one metorite that came from the moon).

Sorry, can't tell you anything about the rarest mineral(s). There are a few wildly unstable radioactive elements such as Technetium which last only fractions of a second, and exist on earth in only fractions of a gram. Astatine is the rarest naturally occurring element, with less than 30 grams (1.058 ounces) estimated to be contained in the entire Earth's crust. Can't tell you about the artificial elements, such as Plutonium, and in fact, Astatine is sometimes created artificially for research. If you're interested, there are isotopes of stable elements, some of which are not only very rare, but very valuable, such as the Hydrogen isotope Deuterium (it has a neutron, most Hydrogen atoms just a proton) and is used in nuclear reactors as a neutron source. Thing is, unfortunately, too rare a term, is it referring to say animals, some of which are extremely rare.

condrite...usually found on meteorites from the kyper belt,,,i think

Your beauty is sweetheart

francium 340 to 550 grams of in the earth's crust at any one time.

Francium and Caesium. Because they are so reactive there is none (that we know of) on the planet.