Separation
When collecting sand on the beach the first step for finding magnetite is to separate it from impurities. Those impurities include sand and any other substances on the beach. This process involves a sieve or some other device. A small device works fine to separate the particles.
Magnet
Once you have the separated particles, to ensure you have only magnetite hold a magnet over the substance. The magnetite particles should move up towards the magnet due to the attraction. Any non-magnetite particles will remain in the pile. Hold the magnet close enough so the attraction will separate the particles. If you do not have a sieve you can use this method for separation.
Paper
This method of purification works well for small projects or on a commercial basis. Place the particles on a piece of paper or a sheet. The size of the paper or sheet depends upon the size of the particles. Run a magnet underneath and watch the magnetite gravitate towards the spots that were magnetized. You will see lines of magnetite.
Steel Wool
Place steel wool in a tube and it will attract magnetite due to the magnetic quality. The steel wool must be magnetized in order for this method to work. This is one more example of magnetic separation.