The "pure element form" of boron is a meteorite. Boron isn't very reactive...but since it's formed by cosmic rays it isn't very abundant either.
It is Black/Brown.
Diamonds are the crystaline form of Carbon.
The most chemically simple form of pure matter is that of a pure element, not chemically bonded in any way.
Neither. It is an element. Also, by definition if a substance is pure it cannot be a mixture; it mus either be an element or a compound.
gold
An element.
No, graphite is a pure substance. It is a form of the pure element carbon.
Yes, californium is a pure chemical element, not a compound or mixture.
most noble gases exist in their pure form because they are so unreactive
Pure substance; it is one form of pure carbon.
Mineralogists call an element that occurs naturally in its pure form uncombined with other elements a native element. These elements are typically found in nature in their pure metallic form, such as gold, silver, and copper.
Neither. Oxygen is an element, which is a pure substance and not a mixture.