Upon encountering a lucky stone on the Downs, some believed that spitting through the hole before casting it over their left shoulder would bring them luck.

Note that felsic rocks are light in color; intermediate rocks range through grays, and mafic rocks are black in color. Ultramafic rocks (peridotite) may range black to olive green (dunite) from the mineral olivine.

Igneous rocks

Here are some suggestions:

1. Check out the tumble stone sections on my website.
2. Check out crystal books.
3. Ask at your local crystal shop.
4. Ask the experts and enthusiasts at your local lapidary club or gem show.
5. Use a pendulum to ask a crystal what it is.
6. Identifying crystals by colour.

An adder stone is a type of stone, usually glassy, with a naturally occurring hole through it.

The Witches Stone, aka: Adder stone or Hag Stone is a type of stone, usually glassy, with a naturally occurring hole through it. Such stones have been discovered by archaeologists in both Britain and Egypt. Commonly, they are found in Northern Germany at the coasts of the North and Baltic Seas.

One stone, known as the “Odin Stone” which stood in the field to the north of the henge, was pierced with a circular hole, and was used by local couples for plighting engagements by holding hands through the gap. It was also associated with other ceremonies and believed to have magical power.

Witches’ stones (in Jèrriais: pièrres dé chorchièrs) are flat stones jutting from chimneys in the islands of Jersey and Guernsey.

We already know from other scholarship that crystal symbolized spiritual purity and perfection and was often used in religious contexts, especially in Christian churches where it was used to decorate Gospel books and other important religious items.

A reciprocal lattice is the periodic set of the wave vectors in reciprocal space that make up the Fourier series of any function. whose periodicity is compatible with that of an initial direct lattice in real space.

For single-crystal XRD, a crystal is mounted and centered within the X-ray beam. For powder XRD, a polycrystalline sample is ground into a fine powder and mounted on a plate. The sample (single- or polycrystalline) is irradiated with X-rays and the diffracted X-rays hit a detector.

XRD peaks are produced by constructive interference of a monochromatic beam of X-rays scattered at specific angles from each set of lattice planes in a sample. The peak intensities are determined by the atomic positions within the lattice planes.

Some steps for performing qualitative analysis of an XRD sample are as follows:

1. Peak identification. The first part of data evaluation is to identify diffraction peaks. This involves several steps:
2. Phase identification. In powder diffraction the term phase is often used as a synonym for substance.