In simplistic terms a common definition for penny stock is less...

In simplistic terms a common definition for penny stock is less than $1 (or $5 in the US) but that simplistic definition ignores market cap and liquidity.

For example, approximately 10 ASX200 companies are trading under $1. One of them, FJX, has a Mcap of about $1.8B and is also a member of the ASX100. Its hard to imagine them as a penny stock.

Then there is the plethera of examples of sub $1 stocks making up the all ords that, IMO, are excellent businesses, have healthy liquidity and are profitable.

Your statement that graphite stocks are a buy under 10c indicates to me that you're measuring value of a company solely on share price and neglecting the fundamental market capitalisation.