The month of June carries three accepted birthstones in the modern American list maintained by the Jewelers of America in cooperation with the American Gem Trade Association: pearl, alexandrite and moonstone. June is one of only three months, with August and December, that has multiple birthstones in the current convention, reflecting both the historical association of June with the pearl and the twentieth-century addition of alexandrite and moonstone.

Pearl

Pearl is the historical June stone, recognised in birthstone lists going back to at least the eighteenth century. Pearls are organic gems formed in molluscs, with a Mohs hardness of around 2.5 to 4.5 and a specific gravity of approximately 2.6 to 2.85. Modern production is dominated by cultured pearls from China, Japan, French Polynesia and Australia, in fresh and saltwater varieties. Pearls are vulnerable to acids, perfumes, hairsprays and ultrasonic cleaning, and are best stored separately from harder stones to avoid surface scratching.

Alexandrite

Alexandrite was added to the American list in 1952 by the Jewelers of America. It is the colour-change variety of chrysoberyl, with a Mohs hardness of 8.5 and a refractive index of approximately 1.746 to 1.755. The stone shows green to bluish-green colour in daylight and red to purplish-red colour in incandescent light. Russian Ural Mountains material from the nineteenth century is the historical reference standard. Modern sources include Brazil, Sri Lanka, Tanzania and India. Genuine fine alexandrite is one of the most expensive coloured stones in the trade per carat in larger sizes.

Moonstone

Moonstone was added as a third June birthstone alongside pearl and alexandrite in the same modern revisions of the American list. It is a variety of orthoclase or oligoclase feldspar showing a soft blue or white sheen, called adularescence, caused by light scattering from internal lamellae. Moonstone has a Mohs hardness of around 6 to 6.5 and is sourced principally from Sri Lanka, India, Madagascar and Burma. Care is conservative because of cleavage, with no ultrasonic cleaning recommended.

List position

The combination of pearl, alexandrite and moonstone covers a wide range of price points and origins for the June birthstone, from accessible cultured freshwater pearls and moonstone cabochons through to fine alexandrite at the top of the coloured-stone market. The British National Association of Jewellers list gives pearl alone for June, while several older European lists give pearl and alexandrite without moonstone.