The birthstone for July in the modern American list, as published by the Jewelers of America in 1912 and as currently maintained by Jewelers of America in cooperation with the American Gem Trade Association, is the ruby. The ruby has held the July position consistently in the modern Western birthstone tradition for more than a century, and is one of the few months whose stone has not been the subject of a recent expansion or alternative.

The stone

Ruby is the red gem variety of the mineral corundum, an aluminium oxide with a Mohs hardness of 9, a refractive index of approximately 1.762 to 1.770, and a specific gravity around 4.00. Its colour is owed to chromium, which produces both the saturated red hue and, through fluorescence, much of the perceived intensity in incandescent light. Pink corundum is by trade convention treated as pink sapphire rather than ruby in most laboratory practice, although the boundary is not absolute.

Origin and trade

The historical reference point for ruby quality is Burmese material from the Mogok Valley, with Mong Hsu material from the 1990s adding a second important Burmese source. Other significant sources include Mozambique, particularly the Montepuez area discovered in 2009; Madagascar; Thailand; and historically Sri Lanka and Vietnam. Treatment is widespread in the trade, with heat treatment standard, lead-glass filling common in low-grade material, and traditional unheated and untreated stones from Burma and Mozambique commanding very large premiums.

Care

Ruby is durable enough for daily wear in any standard mounting and is suited to engagement and statement rings, although it is more brittle than its hardness alone would suggest. Ultrasonic cleaning is generally safe for unheated and heated material but is not recommended for lead-glass filled stones, which are vulnerable to thermal shock and to attack by household chemicals. Cleaning with warm soapy water and a soft brush is the safe default for any treated material whose treatment is not specifically known.

List position

The Jewelers of America has not added an alternative July birthstone, in contrast to the recent additions of spinel for August or citrine for November. Ruby therefore stands alone as the modern July stone in the American convention. The British National Association of Jewellers list also gives ruby for July, as does the older Polish list and the modern Hindu Navaratna correspondence with the Sun, of which ruby is the principal Vedic stone.