Thanks phlux,
from what it seems, the leftover from the benzine clean-up is dmt, oxide and rest alkaloids, and it is no surprise that this gives a proper dmt experience.
The benzine soluble thing is purer dmt. The shape of the crystals does not relly mean much since the same substance can be form different crystals if crystallised from different solvents. Can you try to dissolve these rectangular spice in hexane or heptane and see what crystals they form? I would be surprised if they would be rectangular again!
Also, can you find what the benzine solvent contains? crystal formation also incorporates solvent molecules inside its lattice (just as mineral crystals are often composites of many different salts) and it is not always a simple case of evaporation to remove this "residual" solvent molecules, because it is not residual but rather part of the crystal structure and also part of the end-preparation product.
The latter would account for the change in effects (EDIT: ...and the harshness of the smoke). Another test to do would be to dissolve these crystals in alcohol, and let it evaporate. The crystal structure will break and the co-crystallised solvent molecules will be released.
To recap, two things to try from my side;
1. Try to crystallise the rectangular crystals in another solvent, preferably hexane or heptane - do they still crystalise as rectangular?
2. Try to dissolve the rectangular crystals in alcohol, then let alcohol evaporate; you may repeat this 1-2 times - does this change the effect experience to the dtanderd dmt experience?