This is a 'slab' of mother generated on a large vinegar tank over about 6 months. It is a tough, rubbery, slippery residue from the aecetic bacterial colony, which is primarily a cellulose material the bacteria generate to provide their environment on the surface of the liquid along with the other 'detritus' of the colony, including live and dead bacteria. It is not the healthy part of natural vinegar. Most references to "mother" are probably talking about the bacteria, which of course are invisible. It may [or may not] be beneficial to consume the live aecetic bacteria, but the 'refuse' generated by those bacteria over time isn't what we like on our salad! Our Apple Cider Vinegar is always filtered to crystal clarity, though exposure to the air may allow the bacteria still present to begin working again and generating the first wispy strings of new 'mother', which may be removed by simply pouring the product through a couple layers of cheesecloth.