FreeShip- Feldspar Chunks, Pink-Orange, ~7 to 20 mm, Median ~12mm- (Prompt rebate on orders with 3 or more FreeShip items!)

DESCRIPTION-> Click "Learn more about this item" for article & instructions!
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This is an offering of crushed feldspar that has been separated into groups of sizes ("screened"). It's for experiments in ceramics (Shigaraki or other; feel free to crush to smaller sizes), and a subject for the metaphysician (a student of the metaphysical, and thus of the meta-properties of crystals and minerals; the older term is metaphysicist), also for mineral resin embedments, craft and orgonic alike. This particular feldspar is probably orthoclase, a K-Spar.

The shapes are elongated or blocky, tending to be angular and split along crystalline faces. Orange/pink colors dominate with some pale green and just a little white, green, and dark specks. Feldspar is the primary mineral but there are a few bits of others, such as mica. When small pieces are included in a clay body, and a ceramic piece is fired the chunks melt or semi-melt and show up as part of the ceramic body as spots of color or erupting bumps depending on the clay, feldspar, and the firing temperature. Or they can modify part of the glaze if there is one. Granite chunks are another popular inclusion in the Japanese ceramic style of shigaraki.

There isn't a lot of info about this on the internet. Some forum threads on Ceramic Arts Network referencing "Shigaraki" pottery (Shigaraki is a region in Japan) can be found. Here's a link to an article on Japanese ceramics with feldspathic inclusions:
{ https://ceramicartsnetwork.org/pottery-making-illustrated/article/shigaraki-surfaces/# }
"Shigaraki: A pottery and stoneware made in the Shigaraki region of Japan. Wares from this region are known for containing large feldspar inclusions in the clay body that melt and swell during the firing process."
Here's another thread in Ceramic Arts Daily way back in 2011 about using this effect:
{ http://community.ceramicartsdaily.org/topic/998-firing-rocks-with-clay-sculptures/ }. This is not only used in sculpture but in thrown ware. Sharp chunks can be a little hard on the hands, but not as much as you'd think.
More from Ceramic Arts Daily: { http://community.ceramicartsdaily.org/topic/4634-feldspar-chunks/ }.
Here's a related article: { https://www.quora.com/Is-it-possible-to-integrate-found-objects-such-as-glass-metal-or-previously-fired-ceramics-into-clay-and-fire-it-together }.

Feldspars are common minerals in rocks, making up around 41% of the Earth's crust. There are many types and subtypes of feldspar.
This is a probable "potash spar", widely used in ceramics (and in other areas) for both clay bodies and glazes. This specific potassium feldspar is listed in the Digital Fire ceramics materials database
{ https://digitalfire.com/4sight/material/custer_feldspar_253.html } :
"This is one of the main feldspars used in the ceramic industry in North America. It is used in industries such as abrasives, sanitary ware, floor and wall tile, dinnerware, pottery, and electrical porcelain. It is a ceramic grade, high potash feldspar and is available in crude, 200, 325 mesh and chip form....As with any feldspar, production users should be vigilant to do sieve analysis testing to spot any iron bearing particles in the plus 100 mesh range."

About felspar in general, Digital Fire { https://digitalfire.com/4sight/mineral/ceramic_mineral_feldspar_118.html } says this:
"An indispensable material in the ceramic industry. Most ceramic bodies employ feldspar as a flux to vitrify them at a lower temperature (the feldspar creates a glaze that glues the more refractory particles together to form the fired matrix). Most medium and high temperature glazes employ it as a flux. Feldspars are naturally occurring crystalline rocks that will melt and cool to form a glass. There are many kinds of feldspars, but in ceramics soda, potash and lime feldspars are the most common.
Porcelains can contain up to 50% feldspar, stoneware bodies around 15%. Feldspar sources K2O and Na2O to glazes, these can produce very brilliant results. However, the high KNaO produces a high thermal expansion which in turn produces crazing. Thus it is important to control the amount of feldspar and employ materials that source other low expansion oxides like CaO, MgO, Li2O, BaO, SrO, etc."

Wikipedia lists some other things feldspars are used for { https://en.wikipedia.org/wiki/Feldspar }:
"Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, and resistance to chemical corrosion. In ceramics, the alkalis in feldspar (calcium oxide, potassium oxide, and sodium oxide) act as a flux, lowering the melting temperature of a mixture. Fluxes melt at an early stage in the firing process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and glass fiber. Ceramics (including electrical insulators, sanitary ware, pottery, tableware, and tile) and other uses, such as fillers, accounted for the remainder.
In earth sciences and archaeology, feldspars are used for K-Ar dating, argon-argon dating, and luminescence dating. In October 2012, the Mars Curiosity rover analyzed a rock that turned out to have a high feldspar content."