Asterism is a term which describes “the effect of light rays forming a star (Latin aster, star)…It is usually created through reflection of light by thin fibrous or needle-like inclusions that lie in various directions.” 
Stars in gemstones may have four, six, or (less frequently) twelve rays. With these stones, the angle of the stone to a light source is important to be able to see the star. Natural gemstones known to exhibit asterism include:
star rose quartz
star blue quartz
 Gemstones of the World: Newly Revised & Expanded Fourth Edition by Walter Schumann, p.52
In previous posts, we’ve discussed both sapphires and rubies, which are varieties of corundum. This popular, colorful, and durable gemstone is highly prized.
Corundum is now being diffusion treated with titanium and chromium, where the stone is irradiated to get the colorant to absorb into the outer layer of the stone. Another treatment, beryllium diffusion, has been common for years. Stones treated with any of these methods may lose part or all of their color if the stone is damaged or repolished.
It is possible that there are health hazards from these stone treatments. For example, chromium is toxic and may damage DNA cells.  “There is disturbing evidence that suggests the beryllium treatment poses a health hazard to the workers who process and cut the gemstones and to the merchants who handle them.” 
Surprisingly, irradiated gemstones are generally considered safe because of the mandated cooling off period and monitoring requirements. “NRC [Nuclear Regulatory Commission] requires that the initial distribution of these stones be by a distributor licensed by the NRC. This distributor would conduct radiological surveys of each batch of gemstones to ensure that any residual radioactivity falls below regulatory limits.” 
Sellers in the United States are required by law to disclose all treatments to stones they sell.
The Latin ruber, meaning red, is the likely origin of the name ruby.
Prior to the 1800s, there was not a distinction made between red spinel, red garnet, and ruby. As a result, some of the most famous rubies of the world are not actually rubies. For example, the Black Prince’s Ruby is actually red spinel. There are also a number of misnomers for ruby:
almandine ruby (red garnet)
Australian ruby (red garnet)
balas ruby (red spinel)
Bohemian ruby (red garnet)
cape ruby (red garnet)
Chatham ruby, Ramaura ruby, Linde star ruby are all names describing synthetic, flux grown ruby.
Ruby is a variety of corundum which has a purplish-bluish red to yellow-red color (sapphire is used to describe corundum of any other color). Ruby has a Mohs hardness of 9, making it quite durable and strong.
Clean your ruby jewelry with water mixed with a small amount of mild liquid hand soap with a soft cloth, rinse with water and dry with a soft cloth. You may want to use a toothbrush to clean under the stone. While rubies are not particularly light sensitive, all colored stones can fade with prolonged intense exposure to sunlight, so be sure to store your ruby jewelry out of direct light. As ruby jewelry can last many years, periodically check the prongs and/or settings to be sure the metal is still holding the stone securely in place.
Rubies can have fractures filled with oil, wax, paraffin, glass, or epoxy resin as fillers, reducing the visibility of flaws and cracks within the stone. When this has been done, the ruby is considered to be composite, reducing the value of the stone although the it will look better to the naked eye as the fractures will be nonreflective. Rubies, like sapphires, can also be heat treated to improve the color. Most of the rubies we have seen recently in chain jewelry stores have been lab created rather than natural stones. Sellers are responsible for disclosing all treatments and whether the stone is natural or lab created.
Some of the metaphysical properties associated with ruby include:
shields against negative intentions
guards against psychic or physical attack
helps to be warm, caring toward others
reinvigorates and restores energy
encourages love, passion, joy, spontaneity, laughter, and courage
balances the heart
Chakras: root, heart
 The Jeweler’s Directory of Gemstones by Judith Crowe, p.50