will immediately revert anything
It is safe to handle using thick gloves or tongs.
That is a huge contradiction. You need a better definition of what this thing really does. You seem to go back and forth between it affecting "everything" and it only affecting living things.
Any material expelled from a purified object is found to replace the material taken to replace the missing material.
I really cannot tell what you mean with this sentence. Do you mean that the "impurities" will be separated but still exist? Because your initial description made it sound like the thing is turned into the purest form of whatever the majority of it is. Does a 1kg lump of 80% gold and 20% iron become a 1kg lump of 100% gold, or a .8kg lump of 100% gold and a .2kg lump of 100% iron?
Also, how do you define "purest form"? You mention gold, which is an element; there are gold atoms. Then you mention living beings turning to water, which is a molecule. The human body is comprised of roughly 65% Oxygen atoms in the form of water molecules. Would we not just become Oxygen atoms?
Would this thing not change Earth's entire atmosphere into pure Nitrogen really quickly?
Aside from the above logistical issues, what you have currently is the "thing that does a thing" or "X that does Y" concept. An SCP article is much more than simply an anomalous item, being, place, or event. The true meat of the SCP is the story around the anomalous thing. The thing itself is a vehicle that the narrative is attached to. To give my best example from Series 1, look at SCP 093: The anomalous item itself is a rock that turns mirrors into interdimensional portals. The thing that makes this SCP shine is the story; the history of the dimension that it leads to.
We need to know more than just "it's a rock that changes things to their purest form." What story are you going to tell - How The Foundation found it, Who or what created it and why, did someone use it to some end? (These are not all questions that must be answered, these are some possible narrative hooks.) You need something that differentiates this as an SCP, instead of just an Anomalous Item.
I also recommend reading several (at least 10-20) of the top-rated SCPs from the last several months, and avoid reading series 1 SCPs for inspiration. Many series 1 SCPs would not last a day under current SCP standards, and a few are only still around because of their history with the wiki itself. (This does not apply to all series 1 SCPs, as you can see I mentioned 093 earlier, but many of these were written before the wiki's style had really been cemented.)
The anomalous object, while important, is not actually the main focus of the SCP. A good story, a compelling narrative, something that makes the reader feel something - that is the goal of an SCP article. What feeling do you want to evoke from the reader? Horror? Empathy? Sadness? You need to create a narrative around this object and its effects.
I am not saying this to discourage you, I just want you to understand the amount of effort that goes into creating a successful SCP.
If you can revise this idea with a story that you want to tell, we will be able to give you much more meaningful and constructive critique.
