When the curtain closes on 2018, there's a very good chance it'll go down as the most productive and progressive year in history for the legal marijuana industry.

You might have noticed that many Canadian marijuana stocks have enjoyed nice gains over the past couple of weeks. A huge $4 billion investment by Fortune 500 alcoholic beverage maker Constellation Brands in Canopy Growth produced sympathy moves in several of Canopy's peers. Aphria (NASDAQOTH:APHQF)and Tilray (NASDAQ:TLRY) were two winners by association.

But Tilray has definitely seen greater momentum than Aphria.

 With the legalization date for the recreational sale of cannabis set for October in Canada many cannabis stocks saw significant price moves in the past week. This past week Diageo, a U.K. spirits maker, was in talks with three cannabis producers.

On the back of this information, big players such as Canopy Growth (TSX:WEED) saw its share price jump 33%, driving significant sector returns. Today we have weeded out four-lesser known Canada-listed cannabis stocks with market capitalization under $500 million that saw average returns of at least 30% in the past five trading days

Aurora Cannabis Inc. (TSX:ACB) has been wheeling and dealing during the past year as it looks to make a big splash in the marijuana market. The acquisitions of MedReleaf and CanniMed put the company in a great position to become a leader in that segment. However, it has made great strides since then as well.

Sometimes a first impression doesn't tell the full story. That's the case for my opinion of a small marijuana stock that perhaps hasn't caught the attention of most investors -- CannaRoyalty (NASDAQOTH: CNNRF). 

You have probably read and heard a lot about the top marijuana stocks. For the most part, these are the stocks of Canadian marijuana growers like Canopy Growth (NYSE: CGC). But U.S.-based marijuana businesses don't get nearly as much attention. I'll be the first to admit that I haven't focused on some of these stocks of U.S. companies as much as I have on the Canadian stocks.

One of the most important metrics used in evaluating the success of retailers is revenue per square foot. Apple (NASDAQ:AAPL) reigned as the top retailer in the world last year with $5,546 in revenue per square foot, according to market research company eMarketer. Jewelry store chain Tiffany & Co. was also high on the list with sales of $2,951 per square foot.

But there's now a surprising new winner in this key sales metric. Marijuana retailer MedMen Enterprises (NASDAQOTH:MMNFF) recently reported revenue per square foot of $6,541 at its seven cannabis stores operating in California. And MedMen is just getting started.

Today we have identified five small Canadian stocks in terms of market cap that have experienced a big surge in its stock price coupled with high trading volumes during the past month.

These companies offer investors a potential momentum play.

The five Canada-listed companies identified have seen an average monthly return of 210% and average trading volume of 1.1 million shares per day.

News of another dose of investment from Constellation Brandsin Canopy Growth (TSX:WEED)(NYSE:CGC) in mid-August triggered the latter stock to fly. Specifically, Canopy Growth stock has ascended about 69% since the news. But this wasn’t the only good news that has been pushing the stock to new heights.

This week Canopy Growth’s wholly-owned subsidiary, Tweed, had successfully listed +100 cannabis products in Ontario, including pre-rolled joints, dried flower, oils, and soft-gel capsules. It was ready for October 17, at which time recreational marijuana will be officially legalized in Canada.

Marijuana is already a multibillion-dollar business in the U.S. that’s drawing attention from some lawmakers eager for tax revenue and investors looking for profits. So far, however, some of the biggest insurers are taking a pass.

Allianz SE, Hartford Financial Services Group Inc., and Nationwide Mutual Insurance Co. are among large insurers that aren’t covering marijuana-related businesses. Even as U.S. states increasingly permit the use of pot for medicinal or recreational purposes, the federal government has held fast in keeping weed illegal. That’s driven off name-brand insurers and left the field open for smaller firms.

Whether you realize or not, you'll bear witness to history in less than two months. On Oct. 17, 2018, Canada is set to become the first industrialized country in the world to legalize recreational marijuana. Overall, it'll be only the second country, other than Uruguay, to green-light adult-use pot.