Several small, colourless grains of very rare tachyhydrite in an airtight glass bottle.  Be sure to keep it sealed, as the mineral will dissolve itself in any atmospheric water (hence the name).

1980s material.

Postage combined on multiple orders if you request an invoice BEFORE paying. This avoids eBay charging me their fees twice for overpaid postage.  I will not refund these fees if you pay for multiple items individually without using an invoice - sorry, it is costing me too much money refunding customers postal charges that eBay has taken from me and will not refund! 

International orders over £20 value will be sent via tracked postage.

International postage is quoted for the US, which has increased hugely recently.  Excess P&P (-eBay fees) will be refunded to other locations like Europe.