Shaastra say "bone" is impure, BUT, Conch Shell (Indian Turbinella Pyrum) is super-pure, even to bathe the Deities. Even Lakshmee Devee and Her Lord Naaraayan carry one in Their hands. Shaastra doesn't say any shell or every shell is pure, it's only Indian Shankh (Turbinella Pyrum) that is pure. And these come in two types, normal left side opening AND special right side opening (Valaampuree Dakshin-vartee Turbinella Pyrum). Both are ruled by Goddess Lakshmee. It is not required to have a right-side opening. Left side (normal) opening Shank is perfect for Poojaa. And Lakshmee Shankh is even better than perfect. It is said by Conchologists that only one Lakshmee Shank is found among 1,000 normal Indian Shankh. And ALL Indian Shankh are pure and auspicious.

Ancient scriptures have various references where they classified Shankh broadly into two - right handed and left handed (called sinistral also) and mentioned that right handed are sacred and holy. Here the sizes, shapes, ridges and other micro level details are not narrated, hence one can conclude safely that all right handed Shankh are holy and sacred.

The sinistral shell is coiled in an anti-clockwise direction, so that when viewed from the front (ventral view) with the spire uppermost, the opening or "aperture" appears on the left. Just as the majority of humans are right-handed, gastropod mollusks follow a similar trend and a left-handed shell is something of an oddity. Although there are many species which produce left-handed shells, particularly amongst land snails, they can still look rather strange to the conchologist. They are available in various sizes - from 15 mm to 440 mm.

The Sacred Lakshmee Conch
(sinistral turbinella pyrum). Lakshmee Conch: Dakshin Shankh: The Right-Spiraling Conch Shell. Conch Shells which spiral to the right are very rare and considered especially sacred. The Lakshmee Conch shell is a sacred manifestation of Supreme Goddess Lakshmee, and is most effectively used to bath a genuine Gandakee vajra-kita Shaalgraam Shilaa (ammonite from Gandakee River in Nepal having Chakra cut by Vajra-kita worms 140 million years ago). "Valaampuree" Dakshin Conch and Normal Shank

Fact is this that the left side opening OR the right side opening Turbinella Pyrum Indian Conch - with 3 to 7 ridges in the conch cavity, and special internal structure is the ONLY Shankh that is Vaidik. The normal left-side opening Conch is very low price, even less than the bogus ones (Lightning Whelk), and only the Indian Shankh is correct for Poojaa.

Genuine Vallampuree Lakshmee Shankh (Turbinella Pyrum Conch shells) are sold by gram. Normal size is about 60-120 grams. Depending on quality and number of ridges in the conch cavity they sell for between Rs. 1,000 up to Rs. 3,000 per gram. This means that a genuine Lakshmee Shankh can be had for a few thousand dollars ONLY. So no one has any excuse to use a non-conch shell. Everyone can use either a $2 normal Shankh OR a $2,000 Lakshmee Shankh. But use a Shankh only.

It is far better to use a normal left-handed white smooth Shankh, rather than another type of shell, like a Whelk, that is not even related to a Shankh, and which is NOT recommended as pure. Only a Shankh is auspicious for Poojaa, what to speak of a Shankh that opens on the right side, viz a Lakshmee Shankh. [One can buy genuine Lakshmee Shankh from http://www.salagram.net/sstp-Laxmi-Shank-Club-Global.html]

Heeraa Shankh
All Heeraa Shankh are right handed or Dakshinaavartee. As regards Heeraa Shankh or diamond Shankh, it does not find mention in the scriptures but is worshipped for the merit of the entire inner wall of diamonds or diamond like shining other fossilized crystal or whatever geophysical name it carries technically. this is akin to some rare Shaaligraam which contain gold deposits inside. The quantity of yellow metal inside the Lakshmee Shaaligraam varies and the traces of gold itself inside is considered holy and sacred.