clumping - скопление

clay - глина, глинозем

и вот отзывы об этом продукте -
The box will look like new. It also will not clump all over your litterscoop making it look yucky like clay scoopables do.

But nothing like cleaning a box with clay litter or even a scooping litter. ... The crystals don't get all over nearly as bad as clay litter does. ...

Короче, на основании всех этих результатов поспешного поиска, я осмелюсь предположить, что это что-то глинистое (или может, песок, и вправду), а когда использованное, липкое... хотя... тут Вы уж и сами поймете...

А если вам нужно более конкретно или подробно, и есть время (как раз праздники скоро ;) ) можете поискать сами - просто наберите в любом поисковике эти два слова - информации море, надо только внимательно поискать :))

Feat of clay
The Cat Litter industry has celebrates its 50th anniversary, having been started in 1947 by Ed Lowe, a salesman specialising in industrial absorbents. One of Lowe’s neighbours asked him if he could spare her some sand for her cat’s litter tray. Lowe suggested absorbent dry clay instead, and very soon the neighbour - or rather her cat - would use nothing else.
Ever the entrepreneur, Lowe hit upon the idea of bagging the clay and selling it through pet shops.
Initially, however, Lowe was unsure whether anyone would actually pay for clay while sand was free, so he suggested that, initially, his local pet store should give it away.
Fifty years on, cat litter is still relatively cheap, even so, amazingly, the cat litter industry in the US alone is worth more than $300 million per year.
Apart from clay, cat litters are manufactured from various different materials, all with the same aim of being the most absorbent and providing the best value for money. These are the main types:

Clay based Litter: The oldest and most popular type of cat litter. The clay is coloured grey, white or pink.
* Mostly it ‘clumps’ when wet, thus absorbing urine and the moisture from cats’ faeces. Such clumps can easily be removed from litter trays and disposed of.
* Some brands of clay litter contain an in-built odour
control which is released when wet and masks the smell of
the waste.
* Although clay litters are extremely absorbent, they do tend to be heavy when wet and possibly more difficult to dispose of. They can be added to the garden compost heap, and may be flushed down the toilet... but only in small quantities!

Lightweight Litters:
Nowadays, there are several lightweight litters on the market. These are manufactured from a variety of natural products, such as attapulgite, or sepiolite clay, and are produced in granule form, with the granules varying in size.
* All of the lightweight brands are very absorbent and most boast in-built odour controls. Most do not ‘clump’ in the same way as clay litters, but absorb moisture thoroughly enough.

Wood based Litter: These brands of litter are becoming increasingly popular with cat owners, largely due to their light weight and environmentally-friendly nature.
* Wood-based litters are manufactured from by-products of sawmills, which makes the most of natural resources (i.e. trees). The litter is marketed in the form of small pellets. The wood texture absorbs moisture and releases its own in-built natural odour to mask urine smells.
* The pellets can absorb up to 200 or 300 times their own volume of moisture, thus reaching saturation point very quickly. As it expands such a great deal, it should be used shallowly.
* Wood based cat litter is totally biodegradable and can either be composted, buried or dried out and burned.

Paper-based Litter: A fairly new concept in cat litter, with the litter being manufactured from recycled paper granules. Paper is, of course, very absorbent and soaks up moisture quickly, making the granules expand rapidly. The litter tray can become full very quickly, thus needing frequent emptying.

Fibre-based Litter: Fibre litters are manufactured from natural fibre products, which include dried grass and coconut fibre. Again, these products are very absorbent, usually come with an in-built odour control, but need frequent changing due to their rapid absorbency.
* Both fibre and paper based litters are biodegradable and may be disposed of by composting or by burning once dried out.