Editor’s Note: Some things never change. Especially when those things have been buried beneath the surface of our planet for millions of years.

I thought about that while filling my car with gasoline the other day. The petroleum from which it is made never changes, even though the vehicles into which it goes have evolved enormously since the automobile was invented 140 years ago.

That’s why I believe hard assets should be part of a diversified portfolio. They will always be in demand and there is a limited supply.

As Mark Twain purportedly once said about real estate investing, “Buy land, because they’re not making it anymore.” The same sentiment can also be applied to most other hard assets, some of which appear poised to appreciate rapidly once the economy is back on track.

Silver

I explained my investment thesis for silver last week (“A Silver Lining to the Trump Trade Wars”), so I won’t repeat myself here other than to say that the rapidly rising price of gold might soon trigger a silver rush. Gold has appreciated nearly 50 percent over the past year, driving its price up to an all-time high above $3,400 an ounce at the start of last week.

Unlike gold, silver has many commercial uses that provide a steady level of demand for it. In addition to jewelry, silver is used in automobile engines, solar energy panels, and medical equipment. If gold speculators start taking an interest in silver, that development alone could drive its price considerably higher since the supply of new silver is fairly constant.

The easiest way to participate in the price of silver is via the iShares Silver Trust (NYSE: SLV), which is managed to replicate the daily price movement of silver bullion. For that reason, SLV has gained no ground over the past six months so it’s not too late to get in on the next silver rush.

Petroleum

How often do you hear an old timer (like me) say something like, “I remember when gasoline cost only 50 cents a gallon!” I started buying gasoline in 1975 when I became old enough to drive a car.

Gasoline still only costs 50 cents a gallon if I adjust for inflation over the past fifty years. Even better, cars get considerably better mileage now compared to then so the per vehicle mile cost of gasoline has gone down on an inflation-adjusted basis.

However, crude oil prices have a nasty habit of soaring or tanking suddenly due primarily to changes in global supply and demand for gasoline. And with gasoline prices currently lower now than they’ve been in four years, this may be a good time to buy shares of the ProShares K-1 Free Crude Oil ETF (CBOE: OILK).

This fund is managed to “track the performance of the Bloomberg Commodity Balanced WTI Crude Oil Index.” Its share price has fallen this year in tandem with oil prices, but that could suddenly reverse once the trade wars are over and global commerce gets back to normal.

Uranium

The investment case for uranium relies heavily on the nuclear energy sector, which in this country has been all but dormant since the 3 Mile Island partial reactor meltdown in 1979. That may soon change now that the Trump administration is calling the shots.

Trump’s appointment as Energy Secretary, Chris Wright, is an oil industry executive. Until accepting that appointment, Wright sat on the board of Oklo (NYSE: OKLO), a manufacturer of small nuclear reactors used primarily to power data centers. At the end of last year, Wright reportedly held 2.6 million shares of OKLO.

With the Trump administration withdrawing financial support from renewable energy projects, this country will need an alternative source of fuel to compete with crude oil to keep gasoline prices from rising too high. The obvious candidate is nuclear energy, and when that happens demand for uranium could escalate quickly.

In that case, owning shares of the Global X Uranium ETF (NYSE: URA) would provide exposure to the nuclear energy sector. This fund owns shares of uranium miners, utility companies using nuclear energy, and nuclear power equipment manufacturers including Oklo.