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
The origin of the term “opal” is unclear – it may be from the Roman word opalus, the Sanskrit úpala, the Greek opallios, or any of many other possibilities. In this way, the opal extends its mystery beyond the well known color play into the name of the stone itself.
Natural opal has a lot of variety, including: white opal, black opal, jelly opal, boulder opal, opal matrix, fire opal, harlequin opal, crustal opal, Andean opal, Ethiopian opal, and common opal. White and black opal are most commonly found and these typically display the gorgeous color play which from “the diffraction of light off tiny, closely packed silica spheres inside the stone.”  The silica gel inside the stone is 5-30% water. Most of the world’s natural opals today come from Australia – particularly Lightning Ridge (black opal) and Cooper Pedy (white opal).
Because opal is soft (5.5-6.5 on the Mohs scale), it is often sold as doublets or triplets, which provide color enhancement as well as some protection for the stone. There are also synthetic man-made opals, like Gilson opal and opalite. Be sure to ask your seller for information about any stone you purchase.
Opal can be easily damaged by pressure and impact. Opal is also sensitive to acids and alkalis because of its porous nature, which also makes it vulnerable to perfumes, soaps and detergents. Jewelry should always be removed before washing or applying lotions and other similar products.
If an opal is allowed to dry, it will crack and craze. In most cases, opals do not need any special care while stored. However, if you live in a very dry climate, or keep opals in a dehumidified room, some precautions are necessary. Keeping them in a tight plastic bag, with a damp piece of cotton or fabric will prevent dehydration.
Opals do not mind being hot or cold, it is the rate of change that damages them. You need to avoid exposing the stone to a sudden change in temperature, like from a warm house to the winter’s cold. Simply wearing an opal under clothing will protect it.
Clean your opal with warm or room temperature soap and water. Avoid wearing the stone where it will get rough treatment.
According to lore, opal helps relieve issues with eyesight and was believed to obscure its wearer with a thick fog. 
There are other metaphysical properties ascribed to this multi-colored gem:
Makes it easier to handle changes in life
Protects the wearer from harm
Supports renewal and fidelity in love
Intensifies emotions and intuition
Helps to express your true self
Chakras: links the root and crown
 The Jeweler’s Directory of Gemstones by Judith Crowe, p.92
 A Lapidary of Sacred Stones by Claude Lecouteux, p.244
Tourmalinated (tourmaline included) quartz is a type of quartz that has black or green tourmaline needle-like inclusions within it. The stone looks best when the quartz is clear but more common specimens are found where the quartz is whitish-grey. This uniquely patterned stone has a Mohs hardness of 7, so it is moderately hard but can scratch and get chipped.
Clean your tourmalinated quartz 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. I have a sterling silver and tourmalinated quartz bracelet that I’ve been wearing for 3 or 4 years – the round stones have been unaffected by bathing soaps or shampoo, still looking as lovely as the day I made the bracelet.
Tourmalinated quartz has multiple metaphysical associations with it, including:
excellent protective stone
brings balance and inner strength
deflects and grounds negativity
reduces anxiety and depression
Below is a photo of a tourmalinated quartz trillion. We have a variety of loose gemstones as well as lovely completed pieces at www.dragondreamsjewelry.com.
Although I am normally not a fan of yellow stones, citrine has become one of my favorite crystals.
Citrine is a type of quartz that can be found in shades of yellow to reddish brown, with iron as the primary colorant. Like all quartz, citrine has a Mohs hardness of 7, so it is moderately hard but can scratch and get chipped.
Citrine is sensitive both to heat and sunlight – both could affect the color of the stone. Try to keep your citrine jewelry or stones away from prolonged exposure to intense heat or light and store in a cool, dark place when not in use. Clean your citrine 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.
Many commercial citrines have been heat treated (often from amethyst or smoky quartz). “Almost all heat-treated citrines have a reddish tint. The natural citrines are mostly pale yellow.” Some natural citrines can also have a reddish tint and heat-treated citrines can be a pale lemon yellow.
Citrine has a number of metaphysical associations with it, including:
dissipates negative energies
attracts wealth, success prosperity & abundance
enhances body’s healing energy
opens mind to intuition
helps adapt to change
Chakra: solar plexus
 Gemstones of the World: Newly Revised & Expanded Fourth Edition by Walter Schumann, p.136
“Beads of quartz have been found in caves in Israel that were occupied between 5,000 and 6,000 years ago.” Clearly quartz has been valued over time as a stone of worth for adornment.
There are many varieties of stone in the quartz family. Many are commonly known as quartz: rose quartz, smoky quartz, blue quartz, milky quartz, tourmalinated quartz, rutilated quartz, strawberry quartz, amethyst, and even citrine. However, there are still others less commonly known to be quartz.
Aventurine – usually a milky medium to dark green colored stone but it may be a metallic orange-brown color
Dumortierite quartz – a rare violet-blue to denim-blue colored stone
Prasiolite – a pale green stone that may be anywhere from transparent to translucent; most prasiolite is created by heating amethyst or citrine
Tiger’s eye/hawk’s eye – tiger’s eye has brownish yellow – golden brown/green colors while hawk’s eye has darker blue/black colors; both have the “cat’s eye” effect (chatoyancy) because of the way quartz filled in for the asbestos in the rock fibers as the stone formed
 The Jeweler’s Directory of Gemstones by Judith Crowe, p.67
At a recent show, we were asked about which stone is considered the “angel stone”. Apparently, there are multiple stones which are considered to be helpful for communicating with, contacting, or working with angels. Below are some of the stones I found, along with a very brief description of the angelic attribution for each.
Amethyst: said to have soothing energy that helps connect with angels.
Angelite: the white markings on these blue stones are reminiscent of angel wings; attributes of this stone include bringing awareness to the angelic realms and aiding communication with angels.
Blue lace agate: considered to be helpful for communicating with angels.
Celestite: supposed to provide access to the angelic realms.
Golden danburitie: believed to help one embody angelic wisdom.
Petalite: sometimes called the “stone of the angels” because it is believed to encourage one to demonstrate angelic behavior.
Seraphinite: characterized by feathery marks which may resemble angel wings; said to be helpful facilitating celestial contact.
Angel aura quartz, which is created by finely powdered platinum, silver, and other minerals are bonded to quartz, is also considered to be an angelic stone because the rainbow colors created by the coating seem like angel wings to some.
The following excerpt is from Hildegard von Bingen’s Physica: The Complete English Translation by Priscilla Throop. Hildegard von Bingen, who was canonized as a saint in 2012, lived from 1098-1179 CE. The segment below provides an overview of her beliefs about powers ascribed to gemstones. I hope you enjoy this historical perspective as much as I did.
Every stone contains fire and moisture. The devil abhors, detests, and disdains precious stones. This is because he remembers that their beauty was manifest on him before he fell from the glory God had given him, and because some precious stones are engendered from fire, in which he receives his punishment. By the will of God, the devil was vanquished by the fire into which he fell, just as he is vanquished by the fire of the Holy Spirit when humans are snatched from his jaws by the first breath of the Holy Spirit.
Precious stones and gems arise in the Orient, in areas where the sun’s heat is very great. From the hot sun, mountains there have heat as powerful as fire. The rivers in those areas always boil from the sun’s great heat. Whence at times an inundation of those rivers bursts forth and ascends those scorching mountains. The mountains, burning with the sun’s heat, are touched by those rivers. Froth, similar to that produced by hot iron or a hot stone when water is poured over it, exudes from the places where the water touches the fire. This froth adheres to that place and, in three or four days, hardens into stone.
Once the inundation has ceases and the waters have returned to the river bed, the pieces of froth dry up. They dry from the sun’s heat and take their colors and powers in accordance with the time of day and the temperature. Drying and hardening, they become precious stones and fall onto the sand, just like flaking fish scales. When they flood again the rivers life up many of the stones, carrying them to other countries where they are later discovered by human beings. The mountains, where so many and such large stones have sprung up in this way, shine like the light of day.
And so, precious stones are born from fire and water; whence they have fire and moisture in them. they contain many powers and are effective for many needs. many things can be done with them—but only good, honest actions, which are beneficial to human beings; not activities of seduction, fornication, adultery, enmity, homicide and the like, which tend toward vice and which are injurious to people. The nature of these previous stones seeks honest and useful effects and rejects people’s depraved and evil uses, in the same way virtues cast off vices and vices are unable to engage with virtues.
Some stones do not originate from these mountains and are not of the same nature, but arise from other, useless things. Through them, with God’s permission, it is possible for good and bad things to happen.
God had decorated the first angel as if with precious stones. Lucifer, upon seeing them shine in the mirror of the Divinity, took knowledge from them and recognized that God wished to do many wondrous things. his mind was exalted with pride, since the beauty of the stones which covered him shone in God. he though that he could do deeds both equal to and greater than God’s. And so his splendor was extinguished. But, just as God restored Adam to a better part, He sent neither the beauty nor the powers of those precious stones to perdition, but willed that they would be held in honor and blessing on earth and used for medicine.