Making elemental sulfur from pyrite FeS2
You may just need to heat it.

$$\ce{FeS2 -&gt;[\Delta] FeS + S}$$

In the wikipedia article of pyrite, it is written that:-


  Thermal decomposition of pyrite into $\ce{FeS}$ (iron(II) sulfide) and elemental sulfur starts at 540 °C.


A good experiment for recovering sulfur from iron pyrite is called ' steam-pyrite interactions'.  The following is an excerpt from the original journal:-


  The reactions of natural iron pyrite with steam, hydrogen, and carbon monoxide have been studied in a fixed
  bed tubular reactor at 900-1 100°C. A new process has been developed for the recovery of elemental sulfur
  by the reaction of pyrite with steam. In this process, the yields of elemental sulfur and sulfur evolved as hydrogen
  sulfide and sulfur dioxide were, respectively, 84.5 and 13.7% of total sulfur under the following
  conditions: particle size, below 100 ASTM mesh; temperature, 1000°C; reaction period, 1 5 min; space velocity,
  33.2 X lo4 cc/cc/hr; and partial pressure of steam, 1 atm. Under these conditions, the effluent gas also
  contained an appreciable amount of hydrogen. The calcine contained ferrous oxide, ferrosoferric oxide,
  silica, and 1.3% sulfur. The residual sulfur could be further brought down to a minimum of 0.2% in the calcine
  at 1 100°C using a 30-min reaction period. The incorporation of hydrogen in the steam-iron sulfides reactions
  at 1 100°C increased considerably the yield of hydrogen sulfide (59.5%), but only a small amount of metallic
  iron (1.6%) could be obtained.