Early simulants predated this discovery, but the latest simulant, MGS-1, still does not include them.. Cubic zirconia is crystallographically isometric, an important attribute of a would-be diamond simulant. The mining tests extracted water from lunar regolith simulant that contained ice. Hawaiian volcanic ash has been used as Martian regolith simulant by researchers since 1998. YAG for a period was used in jewelry as a diamond and other gemstone simulant. An effective diamond simulant should therefore be isotropic. From a historical perspective, the most notable natural simulant of diamond is zircon. It also finds use in jewelry as a diamond simulant. The Hawaii tests used both sarin nerve agent and the simulant methylacetoacetate. A second round of tests were run with an anthrax simulant, "Bacillus globigii". A diamond simulant may be artificial, natural, or in some cases a combination thereof. These first rounds of testing utilise water as a propellant simulant. This was tested on Earth with lunar simulant in a vacuum chamber. The test method used the oil/clay (Roma Plastilena) tissue simulant as a test backing. Denis Lill appears as the Simulant Captain and Death.