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Section: October

October — Opal and Tourmaline

Opal and tourmaline — one holds water, the other holds a charge

Opal is delicate and its water content makes it sensitive to dry heat and sudden temperature change. Tourmaline is occasional wear.

3 pieces in this month, ordered by how often they can sensibly be worn — the most forgiving first.

Mineralogy

Opal is hydrated amorphous silica containing 3 to 21 per cent water — not a crystal at all. Its play of colour is diffraction from a regular array of silica spheres. Mohs 5.5 to 6.5. Tourmaline is a complex borosilicate group, Mohs 7 to 7.5, and is pyroelectric: it develops a static charge when heated, which is why loose tourmaline attracts dust.

What the trade does to it

Opal here is untreated. Tourmaline is commonly heated to lighten overly dark material, and every tourmaline on this site is declared heated. Opal doublets and triplets are assembled stones; this site sells solid opal only and says so on the piece.

Documented history

Opal and tourmaline both sit on October on the modern list. Australian opal fields opened in the 1880s and shifted world supply away from the Hungarian deposits that had supplied Europe since Roman times.

October pieces

From £115 · all prices include VAT

Nothing in October reaches Mohs 8, so no piece in this month is graded for daily wear. If the piece needs to be worn every day without special care, look at April, July or September instead. We would rather say that than sell you something that will not survive the way you intend to wear it.

Wear grades in this month

  • Suitable for daily wear

    0 pieces in October

    • Remove before contact sports and heavy manual work
    • Remove before swimming pools and hot tubs — chlorine attacks the metal, not the stone

  • Occasional wear — avoid knocks

    1 piece in October

    • Remove before gym equipment, gardening, DIY and washing up
    • Do not stack against harder stones, which will abrade this one
    • Avoid sudden temperature change

  • Delicate — special occasions only

    2 pieces in October

    • Remove before any physical activity — knocks will chip this stone
    • Keep away from perfume, hairspray, cosmetics and hand sanitiser
    • Avoid sudden temperature change and prolonged dry heat
    • No ultrasonic tank, no steam, no soaking

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