  We report on the discovery of the geometry producing the light echo emanating
from Supernova 2006X, a nearby but underluminous Type Ia in M100 (= NGC 4321).
This offers a rare chance to study the environment of a Type Ia supernova.
Contrary to previous reports, there is little evidence of a circumstellar
component in the light echo morphology or in the light curve of the unresolved
SN point source. Instead, the obvious and dominant echo contribution comes from
what is probably a relatively thin sheet of material some 26 pc in front of SN
2006X. Of the four known Type Ia light echoes, three show no evidence of a
circumstellar echo and the fourth needs to be confirmed. We consider other
evidence for circumstellar material around SN Ia, which may be rare.
