Is Platinum the Hardest Metal?
“Platinum Is the Hardest Metal” and Other Common Misconceptions about the Hardness of Precious Metals
Lots of people assume that platinum is the hardest precious metal. But they are wrong! Although platinum is about two times harder than gold, it is still a relatively soft metal that can be shaped fairly easily. Perhaps the misconception that platinum is very hard has arisen because people confuse tarnish-resistance with hardness. Platinum is extremely tarnish-resistant, yes. But is it also especially hard? No. The fact that it resists tarnishing explains why it can be plated onto silver (which tarnishes easily) to create jewelry that retains its bright surface sheen. But that has nothing to do with hardness.
How Does Platinum’s Hardness Compare to Other Substances?
Fortunately, there is a standard measure of hardness. It’s called the Moh’s Scale of Hardness. It is used to rate the hardness of a variety of substances and elements, not only metals. The softest materials it rates are assigned a rating of 1; the hardest earn a rating of 10.
The softest stuff rated on the Moh’s Scale is talc, a mineral you can crumble easily, using only your fingers. It is assigned a rating of only 1. The hardest substance on the Moh’s scale is the diamond, which rates a ranking of 10.
So, where do different metals rank on the Moh’s Scale? Here’s a list . . .
Gold, silver, zinc and aluminum rank at only between 2.5 and 3
Platinum ranks at 3.5
Iron and nickel rank at 4
Titanium and rhodium rank at 6
And What about Lead?
Lead, which is known to be among the softest of all metals, rates only 1.5 on the Moh’s Scale. And as you know, lead is doggone soft. You can actually make a mark on it using only your fingernail.
Are There Standard Measures of Corrosion Resistance?
That is a logical question to ask. Unfortunately, it is difficult to answer, for a very simple reason . . .
Metals and other substances corrode differently, depending on what they are exposed to
Stainless and other steels, for example, barely oxidize at all when they are exposed to air. But when they are exposed to other substances like some acids, they can corrode much more quickly. So as much as we would like to summarize the corrosion resistance of different metals for you, we cannot; it is far simpler to rate hardness.
One common example? That beautiful new stainless steel kitchen appliance you bought last year, which is now covered with spots and ugly marks. “It is supposed to be stainless steel,” you complain, “how can it get stained?”
It got stained because it was exposed not only to air (which would cause no damage) but to some kind of cleaner or other product that contained a chemical that did the damage.
Do You Have Questions? We Have Answers!
Do you have gold, platinum, palladium, rhodium, or silver scrap? If you do, how can you process it and make money?
Fortunately, that question is not difficult to answer. Call our precious metal recycling consultants at 800-426-2344 and tell us what is on your mind.